Method and system for suppressing stimulated Brillouin scattering effect of gain fiber

Abstract

The invention provides a stimulated Brillouin scattering effect suppression method and system for a gain fiber, and the method comprises the steps: obtaining the frequency spectrum information of stimulated Brillouin scattering (SBS) pulse light, and extracting a Brillouin gain spectrum peak frequency from the frequency spectrum information of the SBS pulse light; calculating the stress of the gain fiber according to the peak frequency of the Brillouin gain spectrum; according to the stress of the gain fiber, determining the degradation condition of the stress by using a frequency stress relational expression; based on the stress degradation condition, the SBS pulsed light is suppressed; according to the invention, the frequency spectrum of the SBS pulsed light is acquired and analyzed in the gain fiber of the wind measurement laser radar, the peak frequency of the Brillouin gain spectrum can be directly extracted, the stress can be calculated, the stress state and the degradation process can be monitored in real time, the SBS pulsed light is inhibited after stress degradation is detected, and the stability of the wind measurement laser radar is improved. Therefore, the SBS effect of the gain fiber can be effectively controlled, thereby facilitating the improvement of the measurement precision and long-term reliability of the wind measurement laser radar.

Description

Technical Field

[0001] The present invention relates to the field of laser radar technology, and in particular to a method and system for suppressing stimulated Brillouin scattering effects of a gain optical fiber. Background Art

[0002] At present, three-dimensional scanning long-distance wind measurement lidar is used for large-scale wind resource assessment in the wind power field, wind shear measurement in the civil aviation field, and wind profile information in the meteorological field due to its large-range, multi-distance layer fine wind field scanning capabilities.

[0003] Figure 1 This is a block diagram of the optical system of a traditional long-range wind measurement lidar. It can achieve a typical line-of-sight detection range of 10 km at a range resolution of 120 m, with single-pulse energy in the hundreds of μJ. A seed laser emits single-frequency light, which is split into two paths by a polarization-maintaining fiber beam splitter: one for the local oscillator and the other for the signal light. The continuous signal light passes through acousto-optic module 1, where it is frequency-shifted and chopped into pulsed light. The light then passes through the first fiber amplifier, amplifying its average power from microwatts to milliwatts. To address pulse leakage caused by insufficient acousto-optic extinction ratio (AOR) of a single pulse, it passes through acousto-optic module 2 for a second frequency shift and chopping, ensuring a 100 dB extinction ratio for the system. The light then passes through the second fiber amplifier, amplifying its average power from tens of milliwatts to hundreds of milliwatts. After filtering out spontaneous emission (ASE) through a bandpass filter, the light enters the third fiber amplifier, which amplifies the power level from hundreds of milliwatts to watts. The light then passes through a polarization-maintaining fiber circulator and is transmitted to the telescope, where it is emitted into the target area. The return light is received by the telescope and transmitted through the circulator again to a 50:50 fiber coupler. Together with the local oscillator light, it is transmitted to the surface of a balanced detector for coherent beat frequency. After photoelectric conversion by a photodiode and amplification by an internal circuit, an analog beat frequency signal is generated.

[0004] In the above system, the third fiber amplifier increases the average laser power from hundreds of milliwatts to watts. Taking a repetition rate of 10 kHz, a pulse width of 500 ns, and an average power of 3.5 W as an example, the peak power will reach 700 W. Such a high peak power will produce severe stimulated Brillouin scattering (SBS) effects in the gain fiber. If the gain fiber of the third fiber amplifier is not processed in any way, part of the energy of the output pulse will be transferred to the frequency-shifted SBS pulse light, and the trailing edge of the signal pulse light will jitter due to energy loss (such as Figure 2 (As shown in the yellow electrical signal waveform), when the jitter pulse is emitted into the atmosphere through the telescope, the jitter in the pulse time domain will cause the jitter of the fixed distance gate of the wind speed measurement, thus causing the wind speed measurement error. Therefore, for the high-energy single-frequency fiber laser of the wind measurement lidar, it is necessary to adjust the gain fiber of the main amplifier stage, that is, Figure 1 The third optical fiber amplifier gain fiber suppresses SBS.

[0005] However, the conventional method to suppress SBS in gain fibers is to use large-mode-field gain fibers and the stress gradient method. The SBS pulse light is reduced by increasing the mode field area of ​​the gain fiber and reducing the SBS gain coefficient. Although the stress gradient method can effectively suppress SBS, it has great application limitations. Wind-measuring lidar works outdoors in a relatively harsh environment. Under complex working conditions, whether the ordinary mechanical stress clamping method can maintain long-term stability under drastic changes in ambient temperature is a technical risk point. Summary of the Invention

[0006] In order to solve the problem in the prior art that during wind measurement, stimulated Brillouin scattering (SBS) pulse light is generated in the gain fiber of the wind measurement lidar, resulting in the SBS effect, which significantly increases the wind speed measurement error and affects the wind measurement accuracy and reliability of the radar, the present invention proposes a method for suppressing the stimulated Brillouin scattering effect of the gain fiber, comprising:

[0007] Acquiring spectrum information of stimulated Brillouin scattering (SBS) pulse light of a gain optical fiber in a wind measurement laser radar, and extracting the Brillouin gain spectrum peak frequency from the spectrum information of the SBS pulse light;

[0008] Calculating the stress of the gain optical fiber according to the Brillouin gain spectrum peak frequency;

[0009] Determining the stress degradation of the gain fiber using a preset frequency-stress relationship according to the stress of the gain fiber;

[0010] Based on the degradation of the stress, the SBS pulse light is suppressed.

[0011] Optionally, the acquiring of spectrum information of stimulated Brillouin scattering (SBS) pulse light of a gain optical fiber in a wind measurement lidar includes:

[0012] Obtain the initial laser emitted by the seed laser in the wind laser radar;

[0013] Splitting the initial laser light into signal light and local oscillator light through a first optical fiber beam splitter;

[0014] Performing frequency shift chopping on the signal light through a first acousto-optic module to obtain a target pulse signal;

[0015] Amplifying the target pulse signal once by a first optical fiber amplifier to obtain a first-stage amplified pulse signal;

[0016] Performing radiation filtering on the first-stage amplified pulse signal through a second acousto-optic module to obtain a processed pulse signal;

[0017] A second optical fiber amplifier is used to amplify the processed pulse signal for a second time to obtain a secondary amplified pulse signal;

[0018] The secondary amplified pulse signal is transmitted to a third optical fiber amplifier through a second optical fiber splitter, and the secondary amplified pulse signal is amplified by the third optical fiber amplifier to obtain a tertiary amplified pulse signal;

[0019] When the power of the three-stage amplified pulse signal in the gain fiber of the third fiber amplifier reaches a preset stimulated Brillouin scattering (SBS) threshold, spectrum information of the stimulated Brillouin scattering (SBS) pulse light is determined based on the three-stage amplified pulse signal.

[0020] Optionally, determining spectrum information of stimulated Brillouin scattering (SBS) pulse light based on the three-stage amplified pulse signal includes:

[0021] Extracting the stimulated Brillouin scattering (SBS) pulse light of the gain optical fiber from the three-stage amplified pulse signal;

[0022] Beating the SBS pulse light with the local oscillator light through a fourth optical fiber beam splitter to obtain a beat signal;

[0023] Converting the beat frequency signal into an electrical signal by a high-speed photodetector to obtain a beat frequency electrical signal;

[0024] A third signal amplification is performed on the beat frequency electrical signal by an intermediate frequency amplifier to obtain a four-stage amplified pulse signal;

[0025] Using a microwave signal generator and a mixer to perform frequency reduction processing on the four-stage amplified pulse signal to obtain a difference frequency signal;

[0026] Signal processing is performed on the difference frequency signal to obtain frequency information of the difference frequency signal, and the frequency information of the difference frequency signal is used as spectrum information of the SBS pulse light.

[0027] Optionally, the down-conversion processing of the four-stage amplified pulse signal using a microwave signal generator and a mixer to obtain a difference frequency signal includes:

[0028] Obtaining a local oscillator signal emitted by a microwave signal generator;

[0029] Performing mixing processing on the local oscillator signal and the four-stage amplified pulse signal through a mixer to obtain a mixed signal;

[0030] Down-conversion processing is performed on the mixed signal to obtain a difference frequency signal.

[0031] Optionally, performing signal processing on the difference frequency signal to obtain frequency information of the difference frequency signal includes:

[0032] amplify the difference frequency signal through a low frequency amplifier to obtain a low frequency amplified signal;

[0033] perform analog-to-digital conversion on the low frequency amplified signal to obtain a digital signal corresponding to the low frequency amplified signal;

[0034] perform analysis on the digital signal by using a signal processing algorithm to obtain frequency information of the difference frequency signal.

[0035] Optionally, the stress calculation formula of the gain optical fiber is as follows:

[0036] ;

[0037] wherein, denotes the stress of the gain optical fiber; denotes the frequency of the local oscillator signal of the microwave signal generator in the wind lidar; denotes the frequency of the SBS pulsed light low frequency difference frequency signal obtained after signal processing; denotes the frequency of the Brillouin gain spectrum peak of the gain optical fiber without stress; denotes a relative coefficient value.

[0038] Optionally, the frequency stress relationship formula is as follows:

[0039] ;

[0040] wherein, denotes the frequency of the Brillouin gain spectrum peak of the gain optical fiber without stress; denotes a relative coefficient value; denotes the stress of the gain optical fiber; denotes the frequency of the Brillouin gain spectrum peak corresponding to the stress of the gain optical fiber.

[0041] Optionally, the SBS pulsed light is suppressed based on the stress degradation, comprising:

[0042] when the stress exists degradation, determining the degradation position and the deviation amount, and adjusting the stress application state based on the degradation position and the deviation amount to obtain a gradient stress, and suppressing the SBS pulsed light according to the gradient stress;

[0043] when the stress does not exist degradation, suppressing the SBS pulsed light according to the stress.

[0044] Based on the same inventive concept, the application further provides a gain optical fiber stimulated Brillouin scattering effect suppression system, comprising:

[0045] ​An information acquisition module is used to obtain the spectrum information of the stimulated Brillouin scattering (SBS) pulse light of the gain fiber in the wind measurement laser radar, and to extract the Brillouin gain spectrum peak frequency from the spectrum information of the SBS pulse light;

[0046] A stress calculation module, configured to calculate the stress of the gain optical fiber according to the Brillouin gain spectrum peak frequency;

[0047] a stress judgment module, configured to determine the stress degradation of the gain optical fiber using a preset frequency-stress relationship according to the stress of the gain optical fiber;

[0048] A pulse suppression module is used to suppress the SBS pulse light based on the degradation condition of the stress.

[0049] Optionally, the information acquisition module includes:

[0050] The laser receiving submodule is used to obtain the initial laser emitted by the seed laser in the wind laser radar;

[0051] a first beam splitting submodule, configured to split the initial laser light into signal light and local oscillator light through a first optical fiber beam splitter;

[0052] a frequency shift chopping submodule, configured to perform frequency shift chopping on the signal light through a first acousto-optic module to obtain a target pulse signal;

[0053] a primary signal amplification submodule, configured to perform primary signal amplification on the target pulse signal through a first optical fiber amplifier to obtain a first-stage amplified pulse signal;

[0054] a radiation filtering submodule, configured to perform radiation filtering on the first-stage amplified pulse signal through a second acousto-optic module to obtain a processed pulse signal;

[0055] a secondary signal amplification submodule, configured to amplify the processed pulse signal for a second time through a second optical fiber amplifier to obtain a secondary amplified pulse signal;

[0056] a main power amplification submodule, configured to transmit the secondary amplified pulse signal to a third optical fiber amplifier via a second optical fiber beam splitter, and perform main power amplification on the secondary amplified pulse signal via the third optical fiber amplifier to obtain a tertiary amplified pulse signal;

[0057] The information confirmation submodule is used to determine the spectrum information of the stimulated Brillouin scattering (SBS) pulse light based on the three-stage amplified pulse signal when the power of the three-stage amplified pulse signal in the gain fiber of the third fiber amplifier reaches a preset stimulated Brillouin scattering (SBS) threshold.

[0058] Optionally, the information confirmation submodule includes:

[0059] a signal extraction unit configured to extract stimulated Brillouin scattering (SBS) pulse light of the gain optical fiber from the three-stage amplified pulse signal;

[0060] a signal beating unit configured to beat the SBS pulse light with the local light through a fourth optical fiber beam splitter to obtain a beating signal;

[0061] a signal conversion unit configured to convert the beating signal into an electric signal through a high-speed photoelectric detector to obtain a beating electric signal;

[0062] a signal amplification unit configured to amplify the beating electric signal for a third time through an intermediate frequency amplifier to obtain a four-stage amplified pulse signal;

[0063] a frequency reduction processing unit configured to perform frequency reduction processing on the four-stage amplified pulse signal through a microwave signal generator and a frequency mixer to obtain a difference frequency signal;

[0064] a signal processing unit configured to perform signal processing on the difference frequency signal to obtain frequency information of the difference frequency signal, and use the frequency information of the difference frequency signal as frequency spectrum information of the SBS pulse light.

[0065] Optionally, the frequency reduction processing unit comprises:

[0066] a local signal acquisition subunit configured to acquire a local signal emitted by the microwave signal generator;

[0067] a frequency mixing processing subunit configured to perform frequency mixing processing on the local signal and the four-stage amplified pulse signal through the frequency mixer to obtain a mixed frequency signal;

[0068] a signal frequency reduction subunit configured to perform frequency reduction processing on the mixed frequency signal to obtain the difference frequency signal.

[0069] Optionally, the signal processing unit comprises:

[0070] a low-frequency amplification subunit configured to amplify the difference frequency signal through a low-frequency amplifier to obtain a low-frequency amplified signal;

[0071] an analog-to-digital conversion subunit configured to perform analog-to-digital conversion on the low-frequency amplified signal to obtain a digital signal corresponding to the low-frequency amplified signal;

[0072] a signal analysis subunit configured to analyze the digital signal through a signal processing algorithm to obtain the frequency information of the difference frequency signal.

[0073] Optionally, a calculation formula of the stress of the gain optical fiber is as follows:

[0074] ;

[0075] in, Represents the stress of the gain fiber; Represents the local oscillator signal frequency of the microwave signal generator in the wind laser radar; is the frequency of the SBS pulse light low-frequency difference frequency signal obtained after signal processing; Indicates the peak frequency of the Brillouin gain spectrum of the gain fiber when no stress is applied; Represents the relative coefficient value.

[0076] Optionally, the frequency-stress relationship is as follows:

[0077] ;

[0078] in, Indicates the peak frequency of the Brillouin gain spectrum of the gain fiber when no stress is applied; Indicates the relative coefficient value; Represents the stress of the gain fiber; The stress of the gain fiber is expressed as The corresponding Brillouin gain spectrum peak frequency.

[0079] Optionally, the pulse suppression module includes:

[0080] a first suppression submodule, configured to, when the stress is degraded, determine a degradation position and a deviation, adjust the stress application state based on the degradation position and the deviation to obtain a gradient stress, and suppress the SBS pulse light according to the gradient stress;

[0081] The second suppression submodule is configured to suppress the SBS pulse light according to the stress when there is no degradation of the stress.

[0082] In another aspect, the present invention further provides an electronic device, comprising: at least one processor and a memory; the memory and the processor are connected via a bus;

[0083] The memory is used to store one or more programs;

[0084] When the one or more programs are executed by the at least one processor, the aforementioned method for suppressing stimulated Brillouin scattering effect of a gain fiber is implemented.

[0085] On the other hand, the present invention further provides a computer-readable storage medium having an execution program stored thereon, which, when executed, implements the method for suppressing stimulated Brillouin scattering effect of a gain fiber as described above.

[0086] Compared with the prior art, the present invention has the following beneficial effects:

[0087] The application provides a stimulated Brillouin scattering effect inhibition method and system of a gain optical fiber, and the method comprises the following steps: acquiring the spectrum information of stimulated Brillouin scattering SBS pulse light of the gain optical fiber in a wind measurement laser radar, and extracting the Brillouin gain spectrum peak frequency from the spectrum information of the SBS pulse light; calculating the stress of the gain optical fiber according to the Brillouin gain spectrum peak frequency; determining the degradation condition of the stress by using a preset frequency stress relationship according to the stress of the gain optical fiber; and inhibiting the SBS pulse light based on the degradation condition of the stress. By acquiring and analyzing the spectrum of the SBS pulse light in the gain optical fiber of the wind measurement laser radar, the Brillouin gain spectrum peak frequency can be directly extracted and the stress can be calculated, which is beneficial to realize the real-time monitoring of the stress state and the degradation process thereof, and the SBS pulse light is further inhibited after the stress degradation is detected, so that the SBS effect of the gain optical fiber is effectively controlled. The process not only can improve the consistency and long-term stability of the stress application, but also can guarantee the waveform integrity and power stability of the output pulse of the fiber laser, thereby significantly reducing the time domain and spatial jitter in the wind speed measurement, and improving the measurement accuracy and long-term reliability of the wind measurement laser radar. BRIEF DESCRIPTION OF DRAWINGS

[0088] Figure 1 The optical system block diagram of the wind measurement laser radar in the prior art is shown in the figure;

[0089] Figure 2 The signal pulse light trailing edge jitter schematic diagram caused by SBS in the prior art is shown in the figure;

[0090] Figure 3 The flowchart of the stimulated Brillouin scattering effect inhibition method of the gain optical fiber provided by the application is shown in the figure;

[0091] Figure 4 The overall framework schematic diagram of the stimulated Brillouin scattering effect inhibition method of the gain optical fiber provided by the application is shown in the figure;

[0092] Figure 5 The spectrum peak frequency schematic diagram of SBS without stress is shown in the figure;

[0093] Figure 6 The spectrum peak frequency schematic diagram of SBS with stress is shown in the figure;

[0094] Figure 7 The structural composition schematic diagram of the stimulated Brillouin scattering effect inhibition system of the gain optical fiber provided by the application is shown in the figure;

[0095] Figure 8 The structural schematic diagram of the electronic device provided by the application is shown in the figure. DETAILED DESCRIPTION

[0096] The present invention provides a method, system, device and medium for suppressing the stimulated Brillouin scattering effect of a gain optical fiber. The specific embodiments of the present invention are further described in detail below with reference to the accompanying drawings.

[0097] Example 1:

[0098] The present invention provides a method for suppressing the stimulated Brillouin scattering effect of a gain optical fiber, the flow chart of which is as follows: Figure 3 Shown, including:

[0099] Step 1: Obtain spectrum information of stimulated Brillouin scattering (SBS) pulse light of the gain fiber in the wind laser radar, and extract the Brillouin gain spectrum peak frequency from the spectrum information of the SBS pulse light;

[0100] Step 2: Calculating the stress of the gain fiber according to the Brillouin gain spectrum peak frequency;

[0101] Step 3: Determine the stress degradation of the gain fiber using a preset frequency-stress relationship according to the stress of the gain fiber;

[0102] Step 4: Suppressing the SBS pulse light based on the stress degradation condition.

[0103] In general, most of the existing SBS pulse light suppression methods rely on passive means, such as using large mode field gain fiber to reduce the SBS gain coefficient, or mechanically applying a stress gradient on the fiber to broaden the Brillouin gain spectrum peak. Although these methods can alleviate the SBS effect to a certain extent, they have the problems of insufficient long-term stability and difficulty in ensuring consistency. In practical applications, the stress on the gain fiber is easily degraded with temperature changes, environmental disturbances or assembly process differences, causing the SBS effect to be re-enhanced, thereby causing pulse waveform distortion and signal trailing edge jitter. In order to solve the above problems, the present invention considers obtaining the spectrum information of the SBS pulse light and extracting the Brillouin gain spectrum peak frequency, and then calculating the stress magnitude in real time in combination with the corresponding relationship between frequency and stress, and using a preset model to judge the stress degradation situation, and finally suppressing the SBS pulse light based on monitoring, thereby avoiding the shortcomings of the prior art of relying heavily on external conditions and having poor long-term reliability.

[0104] In one implementation, the process of obtaining the spectrum information of stimulated Brillouin scattering (SBS) pulse light of the gain fiber in the wind laser radar in step 1 may include:

[0105] Obtain the initial laser emitted by the seed laser in the wind laser radar;

[0106] Splitting the initial laser light into signal light and local oscillator light through a first optical fiber beam splitter;

[0107] Performing frequency shift chopping on the signal light through a first acousto-optic module to obtain a target pulse signal;

[0108] Amplifying the target pulse signal once by a first optical fiber amplifier to obtain a first-stage amplified pulse signal;

[0109] Performing radiation filtering on the first-stage amplified pulse signal through a second acousto-optic module to obtain a processed pulse signal;

[0110] A second optical fiber amplifier is used to amplify the processed pulse signal for a second time to obtain a secondary amplified pulse signal;

[0111] The secondary amplified pulse signal is transmitted to a third optical fiber amplifier through a second optical fiber splitter, and the secondary amplified pulse signal is amplified by the third optical fiber amplifier to obtain a tertiary amplified pulse signal;

[0112] When the power of the three-stage amplified pulse signal in the gain fiber of the third fiber amplifier reaches a preset stimulated Brillouin scattering (SBS) threshold, spectrum information of the stimulated Brillouin scattering (SBS) pulse light is determined based on the three-stage amplified pulse signal.

[0113] In this implementation, the process of determining the spectrum information of stimulated Brillouin scattering (SBS) pulse light based on the three-stage amplified pulse signal may include:

[0114] Extracting the stimulated Brillouin scattering (SBS) pulse light of the gain optical fiber from the three-stage amplified pulse signal;

[0115] Beating the SBS pulse light with the local oscillator light through a fourth optical fiber beam splitter to obtain a beat signal;

[0116] Converting the beat frequency signal into an electrical signal by a high-speed photodetector to obtain a beat frequency electrical signal;

[0117] A third signal amplification is performed on the beat frequency electrical signal by an intermediate frequency amplifier to obtain a four-stage amplified pulse signal;

[0118] Using a microwave signal generator and a mixer to perform frequency reduction processing on the four-stage amplified pulse signal to obtain a difference frequency signal;

[0119] Signal processing is performed on the difference frequency signal to obtain frequency information of the difference frequency signal, and the frequency information of the difference frequency signal is used as spectrum information of the SBS pulse light.

[0120] In this implementation, the process of using a microwave signal generator and a mixer to down-convert the four-stage amplified pulse signal to obtain a difference frequency signal may include:

[0121] Obtaining a local oscillator signal emitted by a microwave signal generator;

[0122] Performing mixing processing on the local oscillator signal and the four-stage amplified pulse signal through a mixer to obtain a mixed signal;

[0123] Down-conversion processing is performed on the mixed signal to obtain a difference frequency signal.

[0124] In this implementation, the process of performing signal processing on the difference frequency signal to obtain frequency information of the difference frequency signal may include:

[0125] A low-frequency amplifier is used to amplify the difference frequency signal to obtain a low-frequency amplified signal;

[0126] Performing analog-to-digital conversion on the low-frequency amplified signal to obtain a digital signal corresponding to the low-frequency amplified signal;

[0127] Analyzing the digital signal using a signal processing algorithm (such as spectrum analysis, peak detection, etc.) to obtain frequency information of the difference frequency signal;

[0128] Specifically, the overall framework diagram for obtaining the spectrum information of SBS pulse light is as follows: Figure 4As shown, the seed laser is split into two beams by a first fiber splitter: one for the local oscillator (LO) and the other for the signal light. The signal light is frequency-shifted and chopped by a first acousto-optic module before being transmitted to a first fiber amplifier for small-signal amplification, increasing the average power from the μW level to the mW level. The amplified signal light then passes through a second acousto-optic module, which improves the extinction ratio of the pulses while filtering out inter-pulse ASE light, thereby enhancing the side-mode suppression ratio (SMSR) of the output signal light. It then passes through a second fiber amplifier, amplifying the average power from tens of mW to hundreds of mW. The amplified signal light passes through a second fiber splitter and then a third fiber amplifier for main power amplification, increasing the power level from hundreds of mW to the watt level. When the signal light pulse reaches the SBS threshold in the gain fiber of the third amplifier, it generates a backward-propagating SBS pulse light, which is transmitted from the second fiber splitter to the input of the fourth fiber splitter. To suppress the SBS effect in the gain fiber of the third fiber amplifier, a gradient stress is applied to the gain fiber. The method of the present invention shifts the SBS gain spectrum peak at different lengths of the gain fiber, preventing linear accumulation of SBS pulse light. Based on the preset Brillouin gain spectrum peak frequency and applied stress relationship (also known as the frequency-stress relationship in the present invention), the backward-propagating SBS pulse light generated in the third fiber amplifier passes through the second fiber beam splitter and then to the fourth fiber beam splitter. The seed laser is split into two beams by the first fiber beam splitter. One beam, acting as the signal light, passes through the first acousto-optic module, while the other beam, acting as the local oscillator light, passes through the third fiber beam splitter and splits into two beams. One beam is used to combine with the aerosol frequency-shifted signal received by the circulator. After passing through a 50:50 coupler, a low-frequency balanced detector, ADC2 (analog-to-digital converter), and signal processing module 2, wind speed information is obtained. The other beam beats with the SBS pulse light through the fourth fiber beam splitter and passes through a high-speed photodetector to obtain the beat signal. Because the peak frequency of the SBS pulse light is around 11 GHz, direct sampling places high demands on the acquisition card, so frequency reduction processing is required. The signal is further amplified by an intermediate frequency amplifier and then passes through a microwave mixer. The mixer's local oscillator inputs the local oscillator signal from the microwave signal generator and mixes it with the input beat frequency signal to produce a difference frequency signal. By adjusting the local oscillator frequency of the microwave signal generator (for example, f0), the frequency of the difference frequency signal is adjusted to an appropriate value. After amplification by a low-frequency amplifier and passing through the ADC1 and signal processing 1 modules, the spectrum information of the SBS pulse light (for example, f1) is obtained.

[0129] By incorporating beat frequency technology and electrical down-conversion processing, this implementation eliminates the need to directly acquire high-frequency SBS pulse signals in the 11 GHz range. Instead, these signals are analyzed in the low-frequency range, significantly reducing the hardware cost and bandwidth requirements for ADC acquisition and signal processing. Furthermore, the higher sampling rate and faster data processing achieved in the low-frequency range improve the real-time and accuracy of SBS monitoring, enabling the wind lidar to dynamically capture subtle changes in the SBS spectrum during operation.

[0130] After obtaining the Brillouin gain spectrum peak frequency through the above steps, it is necessary to further establish a quantitative relationship between this frequency information and the stress on the gain fiber in order to achieve the conversion from optical signal measurement to mechanical stress quantification. For example:

[0131] The calculation formula for the stress of the gain fiber in step 2 above (i.e., the average stress applied in the gain fiber) can be expressed as follows:

[0132] ;

[0133] in, Indicates the stress of the gain fiber, unit is %; Represents the local oscillator signal frequency of the microwave signal generator in the wind laser radar; is the frequency of the SBS pulse light low-frequency difference frequency signal obtained after signal processing; Indicates the Brillouin gain spectrum peak frequency of the gain fiber when no stress is applied (for example, it can be set to 11 GHz); Indicates the relative coefficient value, for example, it can be 4.6% -1 In this example, the local oscillator signal frequency f0 is combined with the difference frequency signal f1 of the SBS pulse light and is compared with the reference frequency in the stress-free state. By comparing the stress inside the fiber, the actual average stress experienced by the fiber is finally determined. This example transforms the difficult-to-measure stress problem inside the fiber into a frequency problem that is easily measurable. This allows for real-time online stress measurement during normal laser operation, with highly sensitive and repeatable results. More importantly, this approach avoids the complexity and instability associated with external stress sensors and instead directly utilizes the fiber's own SBS effect as an intrinsic detection mechanism, fostering a "self-monitoring-self-feedback" suppression model.

[0134] After obtaining the stress value of the gain fiber through the above steps, it is necessary to further determine the degradation of the stress (i.e., whether it remains stable or has decayed) in order to monitor the effectiveness of the stress loading. Specifically:

[0135] In one implementation, during the stress degradation monitoring of the gain fiber in step 3 above, a preset frequency-stress relationship can be used to compare the real-time measured Brillouin peak frequency with the theoretical model to determine whether the fiber stress has subsided. This method facilitates quantitative determination of stress degradation by directly observing the frequency changes of the spectral peak of the SBS pulse light, transforming the traditional method of relying solely on empirical judgment or indirect speculation into an accurate diagnosis based on optical frequency.

[0136] For example, the frequency-stress relationship can be as follows:

[0137] ;

[0138] in, Indicates the peak frequency of the Brillouin gain spectrum of the gain fiber when no stress is applied; Indicates the relative coefficient value; represents the stress of the gain fiber; The stress of the gain fiber is expressed as The Brillouin gain spectrum peak frequency corresponding to the time; in this example, by comparing the measured stress with the preset theoretical model, the degradation of stress caused by time or environmental changes can be effectively identified, thereby providing a dynamic monitoring method for the long-term operation of the fiber laser, which is conducive to solving the defect that the existing gradient stress method cannot evaluate stress stability. The degradation of the applied stress can be known by monitoring the spectrum peak frequency of the backward transmitted SBS pulse light.

[0139] For example, the peak frequency characteristics of SBS without stress (i.e. the above The trend diagram can be shown as Figure 5 As shown in the figure, it can be seen that the SBS spectrum peak is at 310 MHz when there is no stress, with a spectrum width of 36 MHz. In the spectrum range of 50.0 MHz to 550.0 MHz, the signal power in the other frequency bands is low except for this peak. This shows that the SBS spectrum peak frequency is relatively fixed when there is no stress, concentrated near 310 MHz, the signal energy at the spectrum peak is more prominent, and the surrounding background noise or interference signal power is low. The spectrum peak has a certain frequency concentration and relative purity, which can reflect the characteristics of the frequency position and power level of the SBS gain spectrum peak in the unstressed state.

[0140] For example, the peak frequency characteristics of SBS when stress is applied (i.e., the above The trend diagram can be shown as Figure 6As shown in the figure, when stress is applied, the SBS spectrum peak appears at 350 MHz, which is obviously shifted compared to the frequency without stress, and the signal power distribution around the spectrum peak shows more complex changes. The overall spectrum is in the range of 50.0 MHz to 550.0 MHz, the spectrum width is 150 MHz, and the signal power changes with frequency. It is shown that after stress is applied, the frequency of the SBS gain spectrum peak changes greatly, and the energy distribution and other characteristics of the spectrum peak also change correspondingly due to the stress effect, which shows that the stress has a significant impact on the frequency and other characteristics of the SBS spectrum peak, causing the spectrum peak frequency to shift and the spectrum form to be more complex.

[0141] After the stress degradation is accurately identified through the above steps, measures can be taken to maintain the designed stress distribution according to the stress degradation, so as to ensure that the SBS pulsed light is continuously suppressed. Specifically:

[0142] In an implementation manner, the process of suppressing the SBS pulsed light based on the stress degradation in step 4 can include:

[0143] When the stress has degradation, the degradation position and deviation amount are determined, and the stress application state is adjusted based on the degradation position and deviation amount to obtain a gradient stress, and the SBS pulsed light is suppressed according to the gradient stress;

[0144] When the stress has no degradation, the SBS pulsed light is suppressed according to the stress;

[0145] In this implementation manner, by adjusting the stress application state on the basis of stress degradation detection, the optical fiber can be ensured to always maintain the designed gradient stress condition, thereby facilitating to ensure the SBS suppression effect. For example, when stress degradation is detected, the stress distribution is restored by determining the degradation position and deviation amount for targeted adjustment, thereby realizing continuous suppression of the SBS pulsed light. When no degradation is detected, the current stress state is maintained to continue to suppress the SBS effect. Therefore, this implementation manner establishes a linkage mechanism of monitoring and suppression, which is conducive to realizing long-term dynamic maintenance of the SBS suppression effect, thereby being able to improve the stability of the high-power fiber laser in a complex environment.

[0146] In summary, the present invention aims to address the problem that in the operation of existing wind measurement lidars, the SBS effect in the gain fiber causes energy loss and time domain jitter on the trailing edge of the signal pulse light, which in turn significantly increases the wind speed measurement error. A method for suppressing the stimulated Brillouin scattering effect of the gain fiber is proposed. By establishing a corresponding relationship between the stress of the gain fiber and the center frequency of the SBS light, accurate monitoring of the stress relief is achieved, which is beneficial for the life assessment of the fiber laser with gradient stress applied. At the same time, the built-in fiber beam splitter of the laser is used to beat the backward SBS pulse light with the local oscillator light, directly reflecting the changes in the SBS light from the frequency dimension, and converting the spectrum information of about 11 GHz to the low-frequency range through electrical down-conversion, which not only facilitates ADC acquisition and real-time signal processing, but also helps to reduce system costs and improve data processing speed. Compared with the traditional method that only relies on fixed stress application, the present invention can realize real-time monitoring of stress status, timely detect stress degradation, and thus improve the consistency and long-term stability of stress application, effectively improve the yield of fiber lasers, thereby obtaining high-power signal light, and provide a solid guarantee for the stable application of high-power single-frequency fiber lasers in wind measurement radars.

[0147] Example 2:

[0148] The present invention based on the same inventive concept also provides a system for suppressing the stimulated Brillouin scattering effect of a gain optical fiber, the structural composition diagram of which is shown in FIG. Figure 7 Shown, including:

[0149] An information acquisition module is used to obtain the spectrum information of the stimulated Brillouin scattering (SBS) pulse light of the gain fiber in the wind measurement laser radar, and to extract the Brillouin gain spectrum peak frequency from the spectrum information of the SBS pulse light;

[0150] A stress calculation module, configured to calculate the stress of the gain optical fiber according to the peak frequency of the Brillouin gain spectrum;

[0151] a stress judgment module, configured to determine the stress degradation of the gain optical fiber using a preset frequency-stress relationship according to the stress of the gain optical fiber;

[0152] A pulse suppression module is used to suppress the SBS pulse light based on the degradation condition of the stress.

[0153] In one implementation, the information acquisition module may include:

[0154] The laser receiving submodule is used to obtain the initial laser emitted by the seed laser in the wind laser radar;

[0155] a first beam splitting submodule, configured to split the initial laser light into signal light and local oscillator light through a first optical fiber beam splitter;

[0156] a frequency shift chopping submodule, configured to perform frequency shift chopping on the signal light through a first acousto-optic module to obtain a target pulse signal;

[0157] a primary signal amplification submodule, configured to perform primary signal amplification on the target pulse signal through a first optical fiber amplifier to obtain a first-stage amplified pulse signal;

[0158] a radiation filtering submodule, configured to perform radiation filtering on the first-stage amplified pulse signal through a second acousto-optic module to obtain a processed pulse signal;

[0159] a secondary signal amplification submodule, configured to amplify the processed pulse signal for a second time through a second optical fiber amplifier to obtain a secondary amplified pulse signal;

[0160] a main power amplification submodule, configured to transmit the secondary amplified pulse signal to a third optical fiber amplifier via a second optical fiber beam splitter, and perform main power amplification on the secondary amplified pulse signal via the third optical fiber amplifier to obtain a tertiary amplified pulse signal;

[0161] The information confirmation submodule is used to determine the spectrum information of the stimulated Brillouin scattering (SBS) pulse light based on the three-stage amplified pulse signal when the power of the three-stage amplified pulse signal in the gain fiber of the third fiber amplifier reaches a preset stimulated Brillouin scattering (SBS) threshold.

[0162] In this implementation, the information confirmation submodule may include:

[0163] A signal extraction unit, configured to extract the stimulated Brillouin scattering (SBS) pulse light of the gain optical fiber from the three-stage amplified pulse signal;

[0164] a signal beat unit, configured to beat the SBS pulse light with the local oscillator light through a fourth optical fiber beam splitter to obtain a beat signal;

[0165] a signal conversion unit, configured to convert the beat frequency signal into an electrical signal through a high-speed photodetector to obtain a beat frequency electrical signal;

[0166] a signal amplifying unit, configured to amplify the beat frequency electrical signal for a third time through an intermediate frequency amplifier to obtain a four-stage amplified pulse signal;

[0167] A frequency reduction processing unit, configured to perform frequency reduction processing on the four-stage amplified pulse signal using a microwave signal generator and a mixer to obtain a difference frequency signal;

[0168] The signal processing unit is configured to perform signal processing on the difference frequency signal to obtain frequency information of the difference frequency signal, and use the frequency information of the difference frequency signal as the spectrum information of the SBS pulse light.

[0169] In the implementation, the frequency reduction processing unit can comprise:

[0170] a local oscillator acquisition subunit configured to acquire a local oscillator signal emitted by a microwave signal generator;

[0171] a frequency mixing processing subunit configured to perform frequency mixing processing on the local oscillator signal and the four-stage amplified pulse signal through a frequency mixer to obtain a mixed frequency signal;

[0172] a signal frequency reduction subunit configured to perform frequency reduction processing on the mixed frequency signal to obtain a difference frequency signal.

[0173] In the implementation, the signal processing unit can comprise:

[0174] a low-frequency amplification subunit configured to perform low-frequency amplification on the difference frequency signal through a low-frequency amplifier to obtain a low-frequency amplified signal;

[0175] an analog-to-digital conversion subunit configured to perform analog-to-digital conversion on the low-frequency amplified signal to obtain a digital signal corresponding to the low-frequency amplified signal;

[0176] a signal analysis subunit configured to analyze the digital signal by using a signal processing algorithm to obtain frequency information of the difference frequency signal.

[0177] For example, the stress calculation formula of the gain optical fiber can be as follows:

[0178] ;

[0179] wherein, represents the stress of the gain optical fiber; represents the frequency of the local oscillator signal of the microwave signal generator in the wind measurement laser radar; represents the frequency of the SBS pulsed light low-frequency difference frequency signal obtained after signal processing; represents the frequency of the Brillouin gain spectrum peak of the gain optical fiber without stress; represents a relative coefficient value.

[0180] For example, the frequency stress relationship formula can be as follows:

[0181] ;

[0182] wherein, represents the frequency of the Brillouin gain spectrum peak of the gain optical fiber without stress; represents a relative coefficient value; represents the stress of the gain optical fiber; represents the frequency of the Brillouin gain spectrum peak of the gain optical fiber when the stress of the gain optical fiber is .

[0183] In one implementation, the pulse suppression module may include:

[0184] a first suppression submodule, configured to, when the stress is degraded, determine a degradation position and a deviation, adjust the stress application state based on the degradation position and the deviation to obtain a gradient stress, and suppress the SBS pulse light according to the gradient stress;

[0185] The second suppression submodule is configured to suppress the SBS pulse light according to the stress when there is no degradation of the stress.

[0186] Example 3:

[0187] like Figure 8 As shown, the present invention also provides an electronic device, which may be a computer, a single-chip microcomputer, a smart mobile device, or the like. The electronic device in this embodiment may include a processor, a memory, a transceiver component, and the like. The memory, processor, and transceiver component are connected via a bus; the memory may be used to store an execution program, which may include instructions; and the processor may be used to execute the instructions stored in the memory. The memory may also be used to store data, which may be accessed and / or modified during the execution of the instructions.

[0188] The processor may be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. It is the computing core and control core of the terminal, and is suitable for implementing one or more instructions, specifically suitable for loading and executing one or more instructions in a storage medium to implement corresponding method processes or corresponding functions, so as to implement the steps of a method for suppressing the stimulated Brillouin scattering effect of a gain fiber in the above-mentioned embodiment.

[0189] Example 4:

[0190] Based on the same inventive concept, the present invention also provides a readable storage medium, specifically an electronic device-readable storage medium (Memory). The electronic device-readable storage medium is a memory device within the electronic device, used to store programs and data. It is understood that the storage medium herein may include both built-in storage media within the electronic device and, of course, extended storage media supported by the electronic device. The storage medium provides storage space, which stores the terminal's operating system. Furthermore, this storage space also stores one or more instructions suitable for being loaded and executed by a processor. These instructions may be one or more executable programs (including program code). It should be noted that the storage medium herein may be high-speed RAM memory or non-volatile memory, such as at least one disk drive. The processor loading and executing the one or more instructions stored in the storage medium can implement the steps of the method for suppressing stimulated Brillouin scattering in a gain fiber described in the above-mentioned embodiment.

[0191] Those skilled in the art will appreciate that embodiments of the present invention may be provided as methods, systems, or computer program products. Thus, the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to magnetic disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0192] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowcharts and / or block diagrams, as well as combinations of processes and / or blocks in the flowcharts and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowcharts and / or block diagrams. Figure 1 a process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0193] These computer program instructions may also be stored in a computer readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 a process or multiple processes and / or boxes Figure 1the function specified in the one or more blocks.

[0194] These computer program instructions can also be loaded into computer or other programmable data processing devices, so that a series of operation steps are performed on the computer or other programmable data processing devices to generate computer-implemented processes, and the instructions executed on the computer or other programmable data processing devices provide processes for implementing the flow Figure 1 the flow or flows and / or blocks Figure 1 the steps of the function specified in the one or more blocks.

[0195] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the present application, but not to limit the scope of protection, although the present application has been described in detail with reference to the above examples, those skilled in the art should understand: the skilled in the art can make various changes, modifications or equivalent replacements to the specific embodiments of the application after reading the present application, but these changes, modifications or equivalent replacements are all within the scope of protection of the claims.

Claims

1. A method for suppressing stimulated Brillouin scattering effect of a gain optical fiber, characterized in that: include: Acquiring spectrum information of stimulated Brillouin scattering (SBS) pulse light of a gain optical fiber in a wind measurement laser radar, and extracting the Brillouin gain spectrum peak frequency from the spectrum information of the SBS pulse light; Calculating the stress of the gain optical fiber according to the Brillouin gain spectrum peak frequency; Determining the stress degradation of the gain fiber using a preset frequency-stress relationship according to the stress of the gain fiber; Based on the degradation of the stress, the SBS pulse light is suppressed.

2. The method according to claim 1, wherein The method of obtaining spectrum information of stimulated Brillouin scattering (SBS) pulse light of a gain optical fiber in a wind laser radar comprises: Obtain the initial laser emitted by the seed laser in the wind laser radar; Splitting the initial laser light into signal light and local oscillator light through a first optical fiber beam splitter; Performing frequency shift chopping on the signal light through a first acousto-optic module to obtain a target pulse signal; Amplifying the target pulse signal once by a first optical fiber amplifier to obtain a first-stage amplified pulse signal; Performing radiation filtering on the first-stage amplified pulse signal through a second acousto-optic module to obtain a processed pulse signal; A second optical fiber amplifier is used to amplify the processed pulse signal for a second time to obtain a secondary amplified pulse signal; The secondary amplified pulse signal is transmitted to a third optical fiber amplifier through a second optical fiber splitter, and the secondary amplified pulse signal is amplified by the third optical fiber amplifier to obtain a tertiary amplified pulse signal; When the power of the three-stage amplified pulse signal in the gain fiber of the third fiber amplifier reaches a preset stimulated Brillouin scattering (SBS) threshold, spectrum information of the stimulated Brillouin scattering (SBS) pulse light is determined based on the three-stage amplified pulse signal.

3. The method according to claim 2, wherein The determining of spectrum information of stimulated Brillouin scattering (SBS) pulse light based on the three-stage amplified pulse signal includes: Extracting the stimulated Brillouin scattering (SBS) pulse light of the gain optical fiber from the three-stage amplified pulse signal; Beating the SBS pulse light with the local oscillator light through a fourth optical fiber beam splitter to obtain a beat signal; Converting the beat frequency signal into an electrical signal by a high-speed photodetector to obtain a beat frequency electrical signal; A third signal amplification is performed on the beat frequency electrical signal by an intermediate frequency amplifier to obtain a four-stage amplified pulse signal; Using a microwave signal generator and a mixer to perform frequency reduction processing on the four-stage amplified pulse signal to obtain a difference frequency signal; Signal processing is performed on the difference frequency signal to obtain frequency information of the difference frequency signal, and the frequency information of the difference frequency signal is used as spectrum information of the SBS pulse light.

4. The method according to claim 3, wherein The method of using a microwave signal generator and a mixer to down-convert the four-stage amplified pulse signal to obtain a difference frequency signal includes: Obtaining a local oscillator signal emitted by a microwave signal generator; Performing mixing processing on the local oscillator signal and the four-stage amplified pulse signal through a mixer to obtain a mixed signal; Down-conversion processing is performed on the mixed signal to obtain a difference frequency signal.

5. The method according to claim 3, wherein The performing signal processing on the difference frequency signal to obtain frequency information of the difference frequency signal includes: A low-frequency amplifier is used to amplify the difference frequency signal to obtain a low-frequency amplified signal; Performing analog-to-digital conversion on the low-frequency amplified signal to obtain a digital signal corresponding to the low-frequency amplified signal; The digital signal is analyzed using a signal processing algorithm to obtain frequency information of the difference frequency signal.

6. The method according to claim 1, wherein The calculation formula of the stress of the gain fiber is as follows: ； in, represents the stress of the gain fiber; Represents the local oscillator signal frequency of the microwave signal generator in the wind laser radar; is the frequency of the SBS pulse light low-frequency difference frequency signal obtained after signal processing; Indicates the peak frequency of the Brillouin gain spectrum of the gain fiber when no stress is applied; Represents the relative coefficient value.

7. The method according to claim 1, wherein The frequency-stress relationship is as follows: ； in, Indicates the peak frequency of the Brillouin gain spectrum of the gain fiber when no stress is applied; Represents the relative coefficient value; represents the stress of the gain fiber; The stress of the gain fiber is expressed as The corresponding Brillouin gain spectrum peak frequency.

8. The method according to claim 1, wherein The suppressing of the SBS pulse light based on the stress degradation condition includes: When the stress is degraded, determining the degradation position and deviation amount, adjusting the stress application state based on the degradation position and deviation amount to obtain a gradient stress, and suppressing the SBS pulse light according to the gradient stress; When there is no degradation due to the stress, the SBS pulse light is suppressed according to the stress.

9. A system for suppressing stimulated Brillouin scattering effect of a gain fiber, characterized in that: include: An information acquisition module is used to obtain the spectrum information of the stimulated Brillouin scattering (SBS) pulse light of the gain fiber in the wind measurement laser radar, and to extract the Brillouin gain spectrum peak frequency from the spectrum information of the SBS pulse light; A stress calculation module, configured to calculate the stress of the gain optical fiber according to the Brillouin gain spectrum peak frequency; a stress judgment module, configured to determine the stress degradation of the gain optical fiber using a preset frequency-stress relationship according to the stress of the gain optical fiber; A pulse suppression module is used to suppress the SBS pulse light based on the degradation condition of the stress.

10. The system according to claim 9, wherein: The information acquisition module includes: The laser receiving submodule is used to obtain the initial laser emitted by the seed laser in the wind laser radar; a first beam splitting submodule, configured to split the initial laser light into signal light and local oscillator light through a first optical fiber beam splitter; a frequency shift chopping submodule, configured to perform frequency shift chopping on the signal light through a first acousto-optic module to obtain a target pulse signal; a primary signal amplification submodule, configured to perform primary signal amplification on the target pulse signal through a first optical fiber amplifier to obtain a first-stage amplified pulse signal; a radiation filtering submodule, configured to perform radiation filtering on the first-stage amplified pulse signal through a second acousto-optic module to obtain a processed pulse signal; a secondary signal amplification submodule, configured to amplify the processed pulse signal for a second time through a second optical fiber amplifier to obtain a secondary amplified pulse signal; a main power amplification submodule, configured to transmit the secondary amplified pulse signal to a third optical fiber amplifier via a second optical fiber beam splitter, and perform main power amplification on the secondary amplified pulse signal via the third optical fiber amplifier to obtain a tertiary amplified pulse signal; The information confirmation submodule is used to determine the spectrum information of the stimulated Brillouin scattering (SBS) pulse light based on the three-stage amplified pulse signal when the power of the three-stage amplified pulse signal in the gain fiber of the third fiber amplifier reaches a preset stimulated Brillouin scattering (SBS) threshold.

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