A method and system for suppressing stimulated Brillouin scattering in gain optical fibers

Abstract

This invention provides a method and system for suppressing stimulated Brillouin scattering (SBS) effects in gain optical fibers. The method includes: acquiring the spectral information of stimulated Brillouin scattered (SBS) pulse light and extracting the Brillouin gain peak frequency from the SBS pulse light's spectral information; calculating the stress in the gain optical fiber based on the Brillouin gain peak frequency; determining the stress degradation using a frequency-stress relationship based on the stress in the gain optical fiber; and suppressing the SBS pulse light based on the stress degradation. This invention, by acquiring and analyzing the spectrum of SBS pulse light in the gain optical fiber of a wind-measuring lidar, can directly extract the Brillouin gain peak frequency and calculate the stress. This facilitates real-time monitoring of the stress state and its degradation process. Suppressing the SBS pulse light after detecting stress degradation effectively controls the SBS effect in the gain optical fiber, thereby improving the measurement accuracy and long-term reliability of the wind-measuring lidar.

Description

Technical Field

[0001] This invention relates to the field of lidar technology, specifically to a method and system for suppressing stimulated Brillouin scattering effect in gain optical fibers. Background Technology

[0002] Currently, three-dimensional scanning long-range wind measurement lidar, with its large range and multi-distance layer fine wind field scanning capabilities, is applied to 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.

[0003] Figure 1 This is a block diagram of a traditional long-range wind-measuring lidar optical system, capable of achieving a line-of-sight detection range of 10 km with a resolution of 120m and a single-pulse energy in the hundreds of μJ range. A seed laser emits single-frequency light, which is split into two paths by a polarization-maintaining fiber beam splitter: one path serves as the local oscillator, and the other as the signal light. The continuous signal light passes through acousto-optic module 1, where it is frequency-shifted and chopped into pulsed light. Then, it passes through a first fiber amplifier to amplify the average power from microwatts to milliwatts. To address pulse leakage caused by insufficient acousto-optic extinction ratio, it passes through acousto-optic module 2 again for secondary frequency shifting and chopping, ensuring a 100 dB extinction ratio. The average power is then amplified from tens of milliwatts to hundreds of milliwatts by a second fiber amplifier. After being filtered by a bandpass filter to remove spontaneous emission (ASE), it enters a third-stage fiber amplifier, which amplifies the power from hundreds of milliwatts to watts. The light is then transmitted to a telescope via a polarization-maintaining fiber circulator, emitting the laser to the target area. The returning light is received by the telescope and transmitted again through a circulator to a 50:50 fiber coupler, where it is transmitted along with the local oscillator light to the surface of a balanced detector for coherent beat frequency. After photoelectric conversion by a photodiode and amplification by internal circuitry, an analog beat frequency signal is obtained.

[0004] In the above system, the third fiber amplifier boosts the average laser power from the hundreds of mW level to the W level. Taking a repetition frequency 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 a severe stimulated Brillouin scattering (SBS) effect in the gain fiber. If the gain fiber of the third fiber amplifier is not treated in any way, a portion of the output pulse energy will be transferred to the SBS pulse light with a lower frequency, and the trailing edge of the signal pulse light will produce jitter due to energy loss (e.g., Figure 2 The yellow electrical signal waveform shown in the image indicates that when this jitter pulse is emitted into the atmosphere through the telescope, the jitter in the pulse time domain causes jitter in the spatial distance of the wind speed measurement fixed-distance gate, thus leading to wind speed measurement errors. Therefore, for high-energy single-frequency fiber lasers in wind-measuring lidar, it is necessary to adjust the gain fiber of the main amplification stage. Figure 1 The gain fiber of the third fiber amplifier is used for SBS suppression.

[0005] However, conventional methods for suppressing SBS in gain-growth fiber involve using large-mode-area gain fiber and the stress gradient method. This reduces SBS pulse light by increasing the mode area of ​​the gain fiber and decreasing the SBS gain coefficient. While the stress gradient method can effectively suppress SBS, it has significant application limitations. Wind-measuring lidar operates outdoors in harsh environments. Under complex conditions, whether ordinary mechanical stress clamping methods can maintain their hold for extended periods under drastic temperature changes is a technical risk. Summary of the Invention

[0006] To address the problem in existing wind-measuring lidar technologies where stimulated Brillouin scattering (SBS) pulses are generated in the gain fiber during wind measurement, leading to the SBS effect and significantly increasing wind speed measurement errors, thus affecting the accuracy and reliability of the radar, this invention proposes a method for suppressing the stimulated Brillouin scattering effect in the gain fiber, comprising:

[0007] The spectrum information of stimulated Brillouin scattering (SBS) pulse light in the gain fiber of the wind-measuring lidar is obtained, and the Brillouin gain peak frequency is extracted from the spectrum information of the SBS pulse light.

[0008] The stress of the gain fiber is calculated based on the peak frequency of the Brillouin gain spectrum.

[0009] Based on the stress of the gain fiber, the degradation of the stress is determined using a preset frequency-stress relationship.

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

[0011] Optionally, acquiring the spectral information of stimulated Brillouin scattering (SBS) pulses in the gain fiber of the wind-measuring lidar includes:

[0012] Obtain the initial laser emitted by the seed laser in the wind-measuring lidar;

[0013] The initial laser beam is split into signal light and local oscillator light by a first fiber beam splitter;

[0014] The target pulse signal is obtained by frequency shifting and chopping the signal light using the first acousto-optic module.

[0015] The target pulse signal is amplified once by the first fiber optic amplifier to obtain a first-stage amplified pulse signal.

[0016] The first-stage amplified pulse signal is filtered out by radiation using the second acousto-optic module to obtain a processed pulse signal.

[0017] The processed pulse signal is amplified a second time by a second fiber optic amplifier to obtain a second-stage amplified pulse signal.

[0018] The secondary amplified pulse signal is transmitted to the third fiber amplifier through the second fiber beam splitter, and the main power of the secondary amplified pulse signal is amplified by the third fiber amplifier to obtain the tertiary amplified pulse signal.

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

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

[0021] Extract the stimulated Brillouin scattering (SBS) pulse light from the gain fiber from the third-stage amplified pulse signal;

[0022] The SBS pulse light and the local oscillator light are beat frequencyd by a fourth fiber beam splitter to obtain a beat frequency signal.

[0023] The beat frequency signal is converted into an electrical signal using a high-speed photodetector to obtain a beat frequency electrical signal.

[0024] The beat frequency electrical signal is amplified a third time by an intermediate frequency amplifier to obtain a fourth-stage amplified pulse signal.

[0025] The four-stage amplified pulse signal is down-frequency processed using a microwave signal generator and a mixer to obtain a difference frequency signal;

[0026] The difference frequency signal is processed to obtain its frequency information, and the frequency information of the difference frequency signal is used as the spectral information of the SBS pulse light.

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

[0028] Acquire the local oscillator signal emitted by the microwave signal generator;

[0029] The local oscillator signal and the fourth-stage amplified pulse signal are mixed by a mixer to obtain a mixed signal.

[0030] The frequency of the mixed signal is down-converted to obtain the difference frequency signal.

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

[0032] The difference frequency signal is amplified at a low frequency by a low frequency amplifier to obtain a low frequency amplified signal;

[0033] The low-frequency amplified signal is subjected to analog-to-digital conversion to obtain the corresponding digital signal.

[0034] The digital signal is analyzed using signal processing algorithms to obtain the frequency information of the difference frequency signal.

[0035] Optionally, the stress of the gain fiber is calculated using the following formula:

[0036] ;

[0037] in, Indicates the stress in the gain fiber; This indicates the local oscillator signal frequency of the microwave signal generator in the wind-measuring lidar; The frequency of the SBS pulsed light low-frequency difference frequency signal obtained after signal processing; This represents the peak frequency of the Brillouin gain spectrum of the gain fiber when no stress is applied. This represents the relative coefficient value.

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

[0039] ;

[0040] in, This represents the peak frequency of the Brillouin gain spectrum of the gain fiber when no stress is applied. Indicates the relative coefficient value; Indicates the stress in the gain fiber; The stress of the gain fiber is represented by The corresponding peak frequency of the Brillouin gain spectrum.

[0041] Optionally, suppressing the SBS pulsed light based on the stress degradation includes:

[0042] When the stress degrades, the degradation location and deviation amount are determined, and the stress application state is adjusted based on the degradation location and deviation amount to obtain gradient stress. The SBS pulse light is then suppressed according to the gradient stress.

[0043] When the stress does not degrade, the SBS pulse light is suppressed according to the stress.

[0044] Based on the same inventive concept, this invention also provides a stimulated Brillouin scattering effect suppression system for gain optical fibers, comprising:

[0045] The information acquisition module is used to acquire the spectral information of stimulated Brillouin scattering (SBS) pulse light of the gain fiber in the wind-measuring lidar, and extract the Brillouin gain peak frequency from the spectral information of the SBS pulse light.

[0046] The stress calculation module is used to calculate the stress of the gain fiber based on the peak frequency of the Brillouin gain spectrum.

[0047] The stress determination module is used to determine the degradation of the stress based on the stress of the gain fiber using a preset frequency-stress relationship.

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

[0049] Optionally, the information acquisition module includes:

[0050] The laser receiving submodule is used to acquire the initial laser emitted by the seed laser in the wind-measuring lidar.

[0051] The first beam splitting submodule is used to split the initial laser into signal light and local oscillator light through the first fiber beam splitter;

[0052] The frequency-shifting chopper submodule is used to perform frequency-shifting chopping on the signal light through the first acousto-optic module to obtain the target pulse signal;

[0053] A primary signal amplification submodule is used to amplify the target pulse signal through a first fiber optic amplifier to obtain a first-stage amplified pulse signal.

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

[0055] The secondary signal amplification submodule is used to amplify the processed pulse signal a second time through a second fiber optic amplifier to obtain a secondary amplified pulse signal.

[0056] The main power amplifier submodule is used to transmit the secondary amplified pulse signal to the third fiber amplifier through the second fiber beam splitter, and to perform main power amplification on the secondary amplified pulse signal through the third fiber amplifier to obtain the tertiary amplified pulse signal.

[0057] The information confirmation submodule is used to determine the spectral information of the stimulated Brillouin scattering (SBS) pulse light based on the third-stage amplified pulse signal when the power of the third-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] The signal extraction unit is used to extract the stimulated Brillouin scattering (SBS) pulse light of the gain fiber from the three-stage amplified pulse signal.

[0060] The signal beat frequency unit is used to beat the SBS pulse light and the local oscillator light through the fourth fiber beam splitter to obtain a beat frequency signal.

[0061] The signal conversion unit is used to convert the beat frequency signal into an electrical signal using a high-speed photodetector to obtain a beat frequency electrical signal.

[0062] The signal amplification unit is used to amplify the beat frequency electrical signal a third time through an intermediate frequency amplifier to obtain a fourth-stage amplified pulse signal.

[0063] The frequency reduction processing unit is used to reduce the frequency of the four-stage amplified pulse signal using a microwave signal generator and a mixer to obtain a difference frequency signal.

[0064] The signal processing unit is used to perform signal processing on the difference frequency signal to obtain the frequency information of the difference frequency signal, and to use the frequency information of the difference frequency signal as the spectral information of the SBS pulse light.

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

[0066] The local oscillator acquisition subunit is used to acquire the local oscillator signal emitted by the microwave signal generator;

[0067] The mixing processing subunit is used to perform mixing processing on the local oscillator signal and the fourth-stage amplified pulse signal through a mixer to obtain a mixed signal;

[0068] The signal down-frequency subunit is used to down-frequency the mixed signal to obtain the difference frequency signal.

[0069] Optionally, the signal processing unit includes:

[0070] The low-frequency amplification subunit is used to amplify the difference frequency signal at a low frequency through a low-frequency amplifier to obtain a low-frequency amplified signal.

[0071] An analog-to-digital conversion subunit is used 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] The signal analysis subunit is used to analyze the digital signal using signal processing algorithms to obtain the frequency information of the difference frequency signal.

[0073] Optionally, the stress of the gain fiber is calculated using the following formula:

[0074] ;

[0075] in, Indicates the stress in the gain fiber; This indicates the local oscillator signal frequency of the microwave signal generator in the wind-measuring lidar; The frequency of the SBS pulsed light low-frequency difference frequency signal obtained after signal processing; This represents the peak frequency of the Brillouin gain spectrum of the gain fiber when no stress is applied. This represents the relative coefficient value.

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

[0077] ;

[0078] in, This represents the peak frequency of the Brillouin gain spectrum of the gain fiber when no stress is applied. Indicates the relative coefficient value; Indicates the stress in the gain fiber; The stress of the gain fiber is represented by The corresponding peak frequency of the Brillouin gain spectrum.

[0079] Optionally, the pulse suppression module includes:

[0080] The first suppression submodule is used to determine the degradation location and deviation amount when the stress degrades, adjust the stress application state based on the degradation location and deviation amount to obtain gradient stress, and suppress the SBS pulse light according to the gradient stress.

[0081] The second suppression submodule is used to suppress the SBS pulse light according to the stress when the stress does not degrade.

[0082] In another aspect, the present invention also 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, a method for suppressing stimulated Brillouin scattering effect in a gain fiber as described above is implemented.

[0085] In another aspect, the present invention also provides a computer device readable storage medium having an executable program stored thereon, wherein when the executable program is executed, it implements the stimulated Brillouin scattering effect suppression method for a gain fiber as described above.

[0086] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0087] This invention provides a method and system for suppressing stimulated Brillouin scattering (SBS) effects in gain optical fibers, comprising: acquiring the spectral information of stimulated Brillouin scattering (SBS) pulses from the gain optical fiber in a wind-measuring lidar, and extracting the Brillouin gain peak frequency from the spectral information of the SBS pulses; calculating the stress of the gain optical fiber based on the Brillouin gain peak frequency; determining the stress degradation status using a preset frequency-stress relationship based on the stress of the gain optical fiber; and suppressing the SBS pulses based on the stress degradation status. This invention, by acquiring and analyzing the spectrum of SBS pulses in the gain optical fiber of a wind-measuring lidar, can directly extract the Brillouin gain peak frequency and calculate the stress, which is beneficial for real-time monitoring of the stress state and its degradation process. Further suppression of the SBS pulses after detecting stress degradation effectively controls the SBS effect in the gain optical fiber. This process not only improves the consistency and long-term stability of stress application but also ensures the waveform integrity and power stability of the output pulses of the fiber laser, thereby significantly reducing temporal and spatial jitter in wind speed measurement and improving the measurement accuracy and long-term reliability of the wind-measuring lidar. Attached Figure Description

[0088] Figure 1 This is a block diagram of an optical system for wind-measuring lidar in the prior art;

[0089] Figure 2 This is a schematic diagram of the trailing edge jitter of the signal pulse light caused by SBS in the prior art;

[0090] Figure 3 A flowchart illustrating a method for suppressing stimulated Brillouin scattering in gain optical fibers provided by this invention;

[0091] Figure 4 A schematic diagram of the overall framework of a method for suppressing stimulated Brillouin scattering effect in gain optical fiber provided by the present invention;

[0092] Figure 5 This is a schematic diagram of the peak frequencies of the SBS spectrum under no stress.

[0093] Figure 6 This is a schematic diagram of the peak frequencies of the SBS spectrum when stress is applied.

[0094] Figure 7 A schematic diagram of the structure of a stimulated Brillouin scattering suppression system for gain optical fiber provided by the present invention;

[0095] Figure 8 This is a schematic diagram of the structure of an electronic device provided by the present invention. Detailed Implementation

[0096] This invention proposes a method, system, device, and medium for suppressing stimulated Brillouin scattering in gain optical fibers. The specific embodiments of this invention will be further described in detail below with reference to the accompanying drawings.

[0097] Example 1:

[0098] This invention provides a method for suppressing stimulated Brillouin scattering in gain optical fibers, as illustrated in the flowchart below. Figure 3 As shown, it includes:

[0099] Step 1: Obtain the spectral information of stimulated Brillouin scattering (SBS) pulse light from the gain fiber in the wind-measuring lidar, and extract the Brillouin gain peak frequency from the spectral information of the SBS pulse light.

[0100] Step 2: Calculate the stress of the gain fiber based on the peak frequency of the Brillouin gain spectrum;

[0101] Step 3: Determine the stress degradation based on the stress of the gain fiber using a preset frequency-stress relationship.

[0102] Step 4: Based on the degradation of the stress, suppress the SBS pulse light.

[0103] Generally, existing SBS pulse suppression methods mostly rely on passive means, such as using large-mode-field gain fibers to reduce the SBS gain coefficient, or applying stress gradients to the fiber mechanically to broaden the Brillouin gain spectrum peak. While these methods can mitigate the SBS effect to some extent, they suffer from insufficient long-term stability and difficulty in ensuring consistency. In practical applications, the stress on the gain fiber is prone to degradation due to temperature changes, environmental disturbances, or differences in assembly processes, causing the SBS effect to re-enhance, resulting in pulse waveform distortion and signal trailing edge jitter. To address these issues, this invention considers acquiring the spectral information of the SBS pulse and extracting the Brillouin gain spectrum peak frequency. Then, combining the frequency-stress correlation, the stress magnitude is calculated in real time, and a pre-set model is used to determine the stress degradation. Ultimately, based on monitoring, the SBS pulse is suppressed, thus avoiding the shortcomings of existing technologies, such as high dependence on external conditions and poor long-term reliability.

[0104] In one implementation, the process of obtaining the spectral information of the stimulated Brillouin scattering (SBS) pulse light of the gain fiber in the wind-measuring lidar in step 1 above may include:

[0105] Obtain the initial laser emitted by the seed laser in the wind-measuring lidar;

[0106] The initial laser beam is split into signal light and local oscillator light by a first fiber beam splitter;

[0107] The target pulse signal is obtained by frequency shifting and chopping the signal light using the first acousto-optic module.

[0108] The target pulse signal is amplified once by the first fiber optic amplifier to obtain a first-stage amplified pulse signal.

[0109] The first-stage amplified pulse signal is filtered out by radiation using the second acousto-optic module to obtain a processed pulse signal.

[0110] The processed pulse signal is amplified a second time by a second fiber optic amplifier to obtain a second-stage amplified pulse signal.

[0111] The secondary amplified pulse signal is transmitted to the third fiber amplifier through the second fiber beam splitter, and the main power of the secondary amplified pulse signal is amplified by the third fiber amplifier to obtain the tertiary amplified pulse signal.

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

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

[0114] Extract the stimulated Brillouin scattering (SBS) pulse light from the gain fiber from the third-stage amplified pulse signal;

[0115] The SBS pulse light and the local oscillator light are beat frequencyd by a fourth fiber beam splitter to obtain a beat frequency signal.

[0116] The beat frequency signal is converted into an electrical signal using a high-speed photodetector to obtain a beat frequency electrical signal.

[0117] The beat frequency electrical signal is amplified a third time by an intermediate frequency amplifier to obtain a fourth-stage amplified pulse signal.

[0118] The four-stage amplified pulse signal is down-frequency processed using a microwave signal generator and a mixer to obtain a difference frequency signal;

[0119] The difference frequency signal is processed to obtain its frequency information, and the frequency information of the difference frequency signal is used as the spectral information of the SBS pulse light.

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

[0121] Acquire the local oscillator signal emitted by the microwave signal generator;

[0122] The local oscillator signal and the fourth-stage amplified pulse signal are mixed by a mixer to obtain a mixed signal.

[0123] The frequency of the mixed signal is down-converted to obtain the difference frequency signal.

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

[0125] The difference frequency signal is amplified at a low frequency by a low frequency amplifier to obtain a low frequency amplified signal;

[0126] The low-frequency amplified signal is subjected to analog-to-digital conversion to obtain the corresponding digital signal.

[0127] The digital signal is analyzed using signal processing algorithms (such as spectrum analysis, peak detection, etc.) to obtain the frequency information of the difference frequency signal;

[0128] Specifically, a schematic diagram of the overall framework for obtaining the spectral information of SBS pulsed light is shown below. Figure 4As shown, the seed laser is split into two beams by a first fiber optic beam splitter: one beam acts as the local oscillator, and the other acts as the signal beam. The signal beam is frequency-shifted and chopped by a first acousto-optic module before being transmitted to a first fiber optic amplifier for small-signal amplification, increasing the average power from the μW level to the mW level. The amplified signal beam then passes through a second acousto-optic module, increasing the pulse extinction ratio and filtering out inter-pulse ASE light, thus improving the side-mode suppression ratio (SMR) of the output signal beam. It then passes through a second fiber optic amplifier, increasing the average power from the tens of mW level to the hundreds of mW level. The amplified signal beam passes through a second fiber optic beam splitter and then through a third fiber optic amplifier for main power amplification, increasing the power level from the hundreds of mW level to the W level. When the pulsed signal beam reaches the SBS threshold in the gain fiber of the third amplifier, a backward-propagating SBS pulse beam is generated, which is transmitted from the second fiber optic beam splitter and enters the input of a fourth fiber optic beam splitter. To suppress the SBS effect in the gain fiber of the third fiber optic amplifier, gradient stress is applied to the gain fiber. The method of this invention can shift the SBS gain spectrum peak at different lengths of the gain fiber, avoiding the linear accumulation of SBS pulse beams. Based on the preset Brillouin gain spectrum peak frequency and applied stress relationship (i.e., the frequency-stress relationship in this invention), the backward-propagating SBS pulse light generated in the third fiber amplifier is transmitted to the fourth fiber beam splitter after passing through the second fiber beam splitter. The seed laser is split into two beams by the first fiber beam splitter. One beam is used as signal light and passes through the first acousto-optic module. The other beam is used as local oscillator light and is split into two beams by the third fiber beam splitter. One beam is used to beat 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 the SBS pulse light through the fourth fiber beam splitter and passes through a high-speed photodetector to obtain the beat frequency signal. Since the peak frequency of SBS pulsed light is around 11 GHz, direct sampling places too high demands on the acquisition card. Therefore, frequency downsampling is necessary. The signal is further amplified by an intermediate frequency amplifier, then passes through a microwave mixer. The local oscillator signal from the microwave signal generator is input to the mixer's local oscillator terminal, and mixed with the input beat frequency signal to obtain the difference frequency signal. By adjusting the local oscillator frequency of the microwave signal generator (e.g., represented by f0), the frequency of the difference frequency signal is adjusted to a suitable value. After being amplified by a low-frequency amplifier, and then processed by ADC1 and signal processing module 1, the spectral information of the SBS pulsed light (e.g., represented by f1) is obtained.

[0129] The aforementioned implementation, by introducing beat frequency technology and electrical down-conversion processing, eliminates the need to directly acquire high-frequency SBS pulse signals in the 11 GHz range. Instead, it shifts the signal to a lower frequency range for analysis, significantly reducing the hardware cost and bandwidth requirements for ADC acquisition and signal processing. Furthermore, the higher sampling rate and faster data processing in the lower frequency range improve the real-time performance and accuracy of SBS monitoring, enabling the wind lidar to dynamically capture subtle changes in the SBS spectrum during operation.

[0130] After obtaining the peak frequency of the Brillouin gain spectrum through the above steps, it is necessary to further establish a quantitative relationship between this frequency information and the stress experienced by the gain fiber, so as to realize the conversion from optical signal measurement to mechanical stress quantification. Example:

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

[0132] ;

[0133] in, The stress of the gain fiber is expressed in % (%). This indicates the local oscillator signal frequency of the microwave signal generator in the wind-measuring lidar; The frequency of the SBS pulsed light low-frequency difference frequency signal obtained after signal processing; This represents the peak frequency of the Brillouin gain spectrum of the gain fiber when no stress is applied (e.g., it can be set to 11 GHz). This represents a relative coefficient value, for example, 4.6%. -1 In this example, the local oscillator signal frequency f0 is combined with the difference frequency signal f1 of the SBS pulsed light, and then compared with the reference frequency under stress-free conditions. By comparing the results, the average stress actually borne by the optical fiber is obtained. Therefore, this example transforms the stress problem, which is difficult to measure directly inside the optical fiber, into a frequency problem that is easy to measure, enabling real-time online stress measurement during normal laser operation. The measurement results are highly sensitive and repeatable. More importantly, this method avoids the complexity and instability of external stress sensors, and instead directly utilizes the SBS effect of the optical fiber itself as an intrinsic detection mechanism, which is conducive to forming a "self-monitoring-self-feedback" suppression mode.

[0134] After obtaining the stress value of the gain fiber through the above steps, it is necessary to further determine the degradation status of the stress (i.e., whether it remains stable or has attenuated) in order to monitor the effectiveness of 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 fiber stress has decreased. This method, by directly observing the spectral peak frequency change of the SBS pulse light, facilitates the quantitative determination of stress degradation, transforming the traditional method of relying solely on experience or indirect inference into a precise diagnosis based on optical frequency.

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

[0137] ;

[0138] in, This represents the peak frequency of the Brillouin gain spectrum of the gain fiber when no stress is applied. Indicates the relative coefficient value; Indicates the stress in the gain fiber; The stress of the gain fiber is represented by The corresponding Brillouin gain peak frequency; in this example, by comparing the measured stress with the preset theoretical model, the degradation of stress caused by changes in time or environment can be effectively identified, thus providing a dynamic monitoring method for the long-term operation of fiber lasers. This helps to solve the deficiency of existing gradient stress methods in being unable to evaluate stress stability. The degradation of applied stress can be known by monitoring the peak frequency of the back-propagated SBS pulse light.

[0139] For example, the spectral peak frequency characteristics of SBS under no stress (i.e., the above-mentioned) A trend diagram can be shown as follows: Figure 5 As shown in the figure, the SBS spectral peak under stress is at 310 MHz with a spectral width of 36 MHz. Within the frequency range of 50.0 MHz to 550.0 MHz, the signal power is low in the remaining frequency bands, indicating that the SBS spectral peak frequency is relatively fixed under stress, concentrated around 310 MHz. The signal energy at the spectral peak is relatively prominent, while the power of surrounding background noise or interference signals is low. The spectral peak exhibits a certain degree of frequency concentration and relative purity, reflecting the frequency position and power level of the SBS gain spectral peak under stress-free conditions.

[0140] For example, the spectral peak frequency characteristics of SBS under applied stress (i.e., the above-mentioned) A trend diagram can be shown as follows: Figure 6As shown in the figure, when stress is applied, the SBS spectral peak appears at 350 MHz, which is significantly different from the frequency when no stress is applied. The signal power distribution around the spectral peak also shows a more complex change. The overall spectrum is in the range of 50.0 MHz to 550.0 MHz with a spectral width of 150 MHz. The signal power fluctuates with frequency, indicating that the frequency of the SBS gain spectral peak changes significantly after stress is applied. At the same time, the energy distribution and other characteristics of the spectral peak also change accordingly due to stress. This shows that stress has a significant impact on the frequency and other characteristics of the SBS spectral peak, causing the spectral peak frequency to shift and the spectral shape to become more complex.

[0141] After accurately identifying the stress degradation through the above steps, measures can be taken to maintain the designed stress distribution, thereby ensuring that the SBS pulse light is continuously suppressed. Specifically:

[0142] In one implementation, step 4 above, which involves suppressing the SBS pulsed light based on the stress degradation, may include:

[0143] When the stress degrades, the degradation location and deviation amount are determined, and the stress application state is adjusted based on the degradation location and deviation amount to obtain gradient stress. The SBS pulse light is then suppressed according to the gradient stress.

[0144] When the stress does not degrade, the SBS pulse light is suppressed according to the stress.

[0145] In this implementation, by adjusting the stress application state based on stress degradation detection, it is possible to ensure that the optical fiber is always maintained under the designed gradient stress conditions, which is beneficial to ensuring the SBS suppression effect. For example, when stress degradation is detected, targeted adjustments are made to restore the stress distribution by determining the degradation location and deviation amount, thereby achieving continuous suppression of SBS pulse light; when no degradation is detected, the current stress state is maintained to continue suppressing the SBS effect. Therefore, by establishing a linkage mechanism between monitoring and suppression, this implementation method is conducive to achieving long-term dynamic maintenance of the SBS suppression effect, thereby improving the stability of high-power fiber lasers operating in complex environments.

[0146] In summary, this invention addresses the problem of significantly increased wind speed measurement errors caused by the SBS effect in the gain fiber of existing wind-measuring lidar, which leads to energy loss and temporal jitter in the trailing edge of the signal pulse light. It proposes a method to suppress the stimulated Brillouin scattering effect in the gain fiber. By establishing a correspondence between the gain fiber stress and the center frequency of the SBS light, accurate monitoring of stress decay is achieved, which is beneficial for lifetime assessment of fiber lasers subjected to gradient stress. Simultaneously, by utilizing the laser's built-in fiber beam splitter, the backward SBS pulse light is beat-frequencyed with the local oscillator light, directly reflecting the changes in the SBS light from a frequency perspective. Furthermore, electrical down-conversion converts the approximately 11 GHz spectral information to a lower frequency range, facilitating ADC acquisition and real-time signal processing, reducing system costs, and improving data processing speed. Compared to traditional methods that rely solely on applying fixed stress, this invention enables real-time monitoring of stress state, timely detection of stress degradation, and thus improves the consistency and long-term stability of stress application. This effectively improves the yield of fiber lasers, resulting in high-power signal light, and provides a solid guarantee for the stable application of high-power single-frequency fiber lasers in wind measurement radar.

[0147] Example 2:

[0148] Based on the same inventive concept, this invention also provides a stimulated Brillouin scattering effect suppression system for gain optical fibers, as shown in the schematic diagram below. Figure 7 As shown, it includes:

[0149] The information acquisition module is used to acquire the spectral information of stimulated Brillouin scattering (SBS) pulse light of the gain fiber in the wind-measuring lidar, and extract the Brillouin gain peak frequency from the spectral information of the SBS pulse light.

[0150] The stress calculation module is used to calculate the stress of the gain fiber based on the peak frequency of the Brillouin gain spectrum.

[0151] The stress determination module is used to determine the degradation of the stress based on the stress of the gain fiber using a preset frequency-stress relationship.

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

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

[0154] The laser receiving submodule is used to acquire the initial laser emitted by the seed laser in the wind-measuring lidar.

[0155] The first beam splitting submodule is used to split the initial laser into signal light and local oscillator light through the first fiber beam splitter;

[0156] The frequency-shifting chopper submodule is used to perform frequency-shifting chopping on the signal light through the first acousto-optic module to obtain the target pulse signal;

[0157] A primary signal amplification submodule is used to amplify the target pulse signal through a first fiber optic amplifier to obtain a first-stage amplified pulse signal.

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

[0159] The secondary signal amplification submodule is used to amplify the processed pulse signal a second time through a second fiber optic amplifier to obtain a secondary amplified pulse signal.

[0160] The main power amplifier submodule is used to transmit the secondary amplified pulse signal to the third fiber amplifier through the second fiber beam splitter, and to perform main power amplification on the secondary amplified pulse signal through the third fiber amplifier to obtain the tertiary amplified pulse signal.

[0161] The information confirmation submodule is used to determine the spectral information of the stimulated Brillouin scattering (SBS) pulse light based on the third-stage amplified pulse signal when the power of the third-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] The signal extraction unit is used to extract the stimulated Brillouin scattering (SBS) pulse light of the gain fiber from the three-stage amplified pulse signal.

[0164] The signal beat frequency unit is used to beat the SBS pulse light and the local oscillator light through the fourth fiber beam splitter to obtain a beat frequency signal.

[0165] The signal conversion unit is used to convert the beat frequency signal into an electrical signal using a high-speed photodetector to obtain a beat frequency electrical signal.

[0166] The signal amplification unit is used to amplify the beat frequency electrical signal a third time through an intermediate frequency amplifier to obtain a fourth-stage amplified pulse signal.

[0167] The frequency reduction processing unit is used to reduce the frequency of 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 used to perform signal processing on the difference frequency signal to obtain the frequency information of the difference frequency signal, and to use the frequency information of the difference frequency signal as the spectral information of the SBS pulse light.

[0169] In this implementation, the frequency reduction processing unit may include:

[0170] The local oscillator acquisition subunit is used to acquire the local oscillator signal emitted by the microwave signal generator;

[0171] The mixing processing subunit is used to perform mixing processing on the local oscillator signal and the fourth-stage amplified pulse signal through a mixer to obtain a mixed signal;

[0172] The signal down-frequency subunit is used to down-frequency the mixed signal to obtain the difference frequency signal.

[0173] In this implementation, the signal processing unit may include:

[0174] The low-frequency amplification subunit is used to amplify the difference frequency signal at a low frequency through a low-frequency amplifier to obtain a low-frequency amplified signal.

[0175] An analog-to-digital conversion subunit is used 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] The signal analysis subunit is used to analyze the digital signal using signal processing algorithms to obtain the frequency information of the difference frequency signal.

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

[0178] ;

[0179] in, Indicates the stress in the gain fiber; This indicates the local oscillator signal frequency of the microwave signal generator in the wind-measuring lidar; The frequency of the SBS pulsed light low-frequency difference frequency signal obtained after signal processing; This represents the peak frequency of the Brillouin gain spectrum of the gain fiber when no stress is applied. This represents the relative coefficient value.

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

[0181] ;

[0182] in, This represents the peak frequency of the Brillouin gain spectrum of the gain fiber when no stress is applied. Indicates the relative coefficient value; Indicates the stress in the gain fiber; The stress of the gain fiber is represented by The corresponding peak frequency of the Brillouin gain spectrum.

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

[0184] The first suppression submodule is used to determine the degradation location and deviation amount when the stress degrades, adjust the stress application state based on the degradation location and deviation amount to obtain gradient stress, and suppress the SBS pulse light according to the gradient stress.

[0185] The second suppression submodule is used to suppress the SBS pulse light according to the stress when the stress does not degrade.

[0186] Example 3:

[0187] like Figure 8 As shown, the present invention also provides an electronic device, which may be a computer device, a microcontroller device, a smart mobile device, etc. The electronic device in this embodiment may include a processor, a memory, a transceiver component, etc. The memory, processor, and transceiver component are connected via a bus; the memory can be used to store executable programs, and an exemplary executable program may include instructions; the processor is used to execute the instructions stored in the memory. The memory can also be used to store data, which can be accessed and / or modified when instructions are executed.

[0188] The processor may be a Central Processing Unit (CPU), or it may be other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. It is the computing and control core of the terminal, and it is suitable for implementing one or more instructions. Specifically, it is suitable for loading and executing one or more instructions in the storage medium to realize the corresponding method flow or corresponding function, so as to realize the steps of the stimulated Brillouin scattering effect suppression method of a gain fiber in the above embodiment.

[0189] Example 4:

[0190] Based on the same inventive concept, this invention also provides a readable storage medium, specifically an electronic device readable storage medium (Memory). This readable storage medium is a memory device within an electronic device used to store programs and data. It is understood that the storage medium here can include both built-in storage media within the electronic device and 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 loading and execution by a processor. These instructions can be one or more executable programs (including program code). It should be noted that the storage medium here can be a high-speed RAM memory or a non-volatile memory, such as at least one disk storage device. Loading and executing one or more instructions stored in the storage medium by the processor can implement the steps of the stimulated Brillouin scattering effect suppression method for a gain fiber in the above embodiments.

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

[0192] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations 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, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0193] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1The function specified in one or more boxes.

[0194] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0195] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit its scope of protection. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that after reading the present invention, they can still make various changes, modifications or equivalent substitutions to the specific implementation methods of the application, but these changes, modifications or equivalent substitutions are all within the scope of protection of the claims pending approval.

Claims

1. A method for suppressing stimulated Brillouin scattering effect in gain optical fibers, characterized in that, include: The method involves acquiring the spectral information of stimulated Brillouin scattering (SBS) pulses from the gain fiber in a wind-measuring lidar, and extracting the Brillouin gain peak frequency from the spectral information of the SBS pulses. Specifically, when acquiring the spectral information of the SBS pulses, the SBS pulses are beat-frequency processed with a local oscillator, and the beat-frequency signal is electrically down-clocked to obtain a difference frequency signal. This difference frequency signal is then processed to obtain the spectral information of the SBS pulses. The stress of the gain fiber is calculated based on the peak frequency of the Brillouin gain spectrum. Based on the stress of the gain fiber, the degradation of the stress is determined using a preset frequency-stress relationship formula; When the stress degrades, the degradation location and deviation amount are determined, and the stress application state is adjusted based on the degradation location and deviation amount to obtain gradient stress. The SBS pulse light is then suppressed according to the gradient stress. When the stress does not degrade, the SBS pulse light is suppressed according to the stress. The formula for calculating the stress of the gain fiber is as follows: ； The frequency-stress relationship is as follows: ； in, Indicates the stress in the gain fiber; This indicates the local oscillator signal frequency of the microwave signal generator in the wind-measuring lidar; The frequency of the SBS pulsed light low-frequency difference frequency signal obtained after signal processing; This represents the peak frequency of the Brillouin gain spectrum of the gain fiber when no stress is applied. Indicates the relative coefficient value; The stress of the gain fiber is represented by The corresponding peak frequency of the Brillouin gain spectrum.

2. The method as described in claim 1, characterized in that, The acquisition of the spectral information of stimulated Brillouin scattering (SBS) pulses in the gain fiber of the wind-measuring lidar includes: Obtain the initial laser emitted by the seed laser in the wind-measuring lidar; The initial laser beam is split into signal light and local oscillator light by a first fiber beam splitter; The target pulse signal is obtained by frequency shifting and chopping the signal light using the first acousto-optic module. The target pulse signal is amplified once by the first fiber optic amplifier to obtain a first-stage amplified pulse signal. The first-stage amplified pulse signal is filtered out by radiation using the second acousto-optic module to obtain a processed pulse signal. The processed pulse signal is amplified a second time by a second fiber optic amplifier to obtain a second-stage amplified pulse signal. The secondary amplified pulse signal is transmitted to the third fiber amplifier through the second fiber beam splitter, and the main power of the secondary amplified pulse signal is amplified by the third fiber amplifier to obtain the tertiary amplified pulse signal. When the power of the third-stage amplified pulse signal in the gain fiber of the third fiber amplifier reaches the preset stimulated Brillouin scattering (SBS) threshold, the spectral information of the stimulated Brillouin scattering (SBS) pulse light is determined based on the third-stage amplified pulse signal.

3. The method as described in claim 2, characterized in that, The determination of the spectral information of the stimulated Brillouin scattering (SBS) pulse light based on the three-stage amplified pulse signal includes: Extract the stimulated Brillouin scattering (SBS) pulse light from the gain fiber from the third-stage amplified pulse signal; The SBS pulse light and the local oscillator light are beat frequencyd by a fourth fiber beam splitter to obtain a beat frequency signal. The beat frequency signal is converted into an electrical signal using a high-speed photodetector to obtain a beat frequency electrical signal. The beat frequency electrical signal is amplified a third time by an intermediate frequency amplifier to obtain a fourth-stage amplified pulse signal. The four-stage amplified pulse signal is down-frequency processed using a microwave signal generator and a mixer to obtain a difference frequency signal; The difference frequency signal is processed to obtain its frequency information, and the frequency information of the difference frequency signal is used as the spectral information of the SBS pulse light.

4. The method as described in claim 3, characterized in that, The step of down-frequency processing the four-stage amplified pulse signal using a microwave signal generator and a mixer to obtain a difference frequency signal includes: Acquire the local oscillator signal emitted by the microwave signal generator; The local oscillator signal and the fourth-stage amplified pulse signal are mixed by a mixer to obtain a mixed signal. The frequency of the mixed signal is down-converted to obtain the difference frequency signal.

5. The method as described in claim 3, characterized in that, The step of processing the difference frequency signal to obtain its frequency information includes: The difference frequency signal is amplified at a low frequency by a low frequency amplifier to obtain a low frequency amplified signal; The low-frequency amplified signal is subjected to analog-to-digital conversion to obtain the corresponding digital signal. The digital signal is analyzed using signal processing algorithms to obtain the frequency information of the difference frequency signal.

6. A system for suppressing stimulated Brillouin scattering in a gain fiber, characterized in that, include: An information acquisition module is used to acquire the spectral information of stimulated Brillouin scattering (SBS) pulse light from the gain fiber in a wind-measuring lidar, and to extract the Brillouin gain peak frequency from the spectral information of the SBS pulse light. Specifically, when acquiring the spectral information of the SBS pulse light, the information acquisition module performs beat frequency processing on the SBS pulse light and the local oscillator light, and then electrically down-clocks the beat frequency signal to obtain a difference frequency signal. The difference frequency signal is then processed to obtain the spectral information of the SBS pulse light. The stress calculation module is used to calculate the stress of the gain fiber based on the peak frequency of the Brillouin gain spectrum. The stress determination module is used to determine the degradation of the stress based on the stress of the gain fiber using a preset frequency-stress relationship. A pulse suppression module is used to suppress the SBS pulse light based on the degradation of the stress. The formula for calculating the stress of the gain fiber is as follows: ； in, Indicates the stress in the gain fiber; This indicates the local oscillator signal frequency of the microwave signal generator in the wind-measuring lidar; The frequency of the SBS pulsed light low-frequency difference frequency signal obtained after signal processing; This represents the peak frequency of the Brillouin gain spectrum of the gain fiber when no stress is applied. Indicates the relative coefficient value; The frequency-stress relationship is as follows: ； in, This represents the peak frequency of the Brillouin gain spectrum of the gain fiber when no stress is applied. Indicates the relative coefficient value; Indicates the stress in the gain fiber; The stress of the gain fiber is represented by The corresponding Brillouin gain spectrum peak frequency; The pulse suppression module includes: The first suppression submodule is used to determine the degradation location and deviation amount when the stress degrades, adjust the stress application state based on the degradation location and deviation amount to obtain gradient stress, and suppress the SBS pulse light according to the gradient stress. The second suppression submodule is used to suppress the SBS pulse light according to the stress when the stress does not degrade.

7. The system as described in claim 6, characterized in that, The information acquisition module includes: The laser receiving submodule is used to acquire the initial laser emitted by the seed laser in the wind-measuring lidar. The first beam splitting submodule is used to split the initial laser into signal light and local oscillator light through the first fiber beam splitter; The frequency-shifting chopper submodule is used to perform frequency-shifting chopping on the signal light through the first acousto-optic module to obtain the target pulse signal; A primary signal amplification submodule is used to amplify the target pulse signal through a first fiber optic amplifier to obtain a first-stage amplified pulse signal. The radiation filtering submodule is used to perform radiation filtering on the first-stage amplified pulse signal through the second acousto-optic module to obtain a processed pulse signal; The secondary signal amplification submodule is used to amplify the processed pulse signal a second time through a second fiber optic amplifier to obtain a secondary amplified pulse signal. The main power amplifier submodule is used to transmit the secondary amplified pulse signal to the third fiber amplifier through the second fiber beam splitter, and to perform main power amplification on the secondary amplified pulse signal through the third fiber amplifier to obtain the tertiary amplified pulse signal. The information confirmation submodule is used to determine the spectral information of the stimulated Brillouin scattering (SBS) pulse light based on the third-stage amplified pulse signal when the power of the third-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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