A narrow bandwidth fiber laser system and method of controlling the same

Abstract

The application relates to the technical field of fiber lasers, and provides a narrow-bandwidth fiber laser system and a control method thereof. The narrow-bandwidth fiber laser system comprises, in sequence, a light source, a first fiber pre-amplification module, a first regulation mechanism, a second fiber pre-amplification module, a second regulation mechanism, a fiber main amplification module and a solid amplification module; the light source is used for outputting laser; the first fiber pre-amplification module is used for pre-amplifying the power of laser; the first regulation mechanism is used for regulating the center wavelength and the spectral width of the pre-amplified laser; the second fiber pre-amplification module is used for twice pre-amplifying the power of laser; the second regulation mechanism is used for regulating the center wavelength and the spectral width of the twice pre-amplified laser; and the fiber main amplification module and the solid amplification module are both used for amplifying the power of laser. The narrow-bandwidth fiber laser system can intelligently, in real time and dynamically, regulate the spectral form and the center wavelength, and realizes high-efficiency narrow-bandwidth laser generation.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of fiber laser, and in particular to a narrow-bandwidth fiber laser system and a control method thereof. BACKGROUND

[0002] Narrow-bandwidth fiber laser is one of the core components of modern photonics. High-power narrow-band fiber seed source is not only the core element to improve the efficiency of traveling wave amplification, but also the key to suppressing harmful nonlinear dynamics such as fractals and chaos in solid-state traveling wave amplifiers, reducing heat generation and maintaining spot quality. However, when the pulse peak power accumulates to a high level in the gain medium such as fiber, it will trigger strong nonlinear optical effects, the most typical of which is self-phase modulation (SPM). SPM will cause significant broadening of the pulse spectrum, resulting in distortion of the seed source output spectrum and increase in bandwidth. In addition, the inevitable thermal effects during the operation of the laser system will cause temperature fluctuations, which will affect the solid-state laser gain medium (such as crystal) and fiber optical elements such as Fiber Bragg Grating (FBG). The emission cross section and refractive index of these materials are sensitive to temperature changes, and temperature fluctuations will cause the laser gain peak to shift and the center wavelength of the optical element to drift, which will cause the laser wavelength to mismatch the optimal extraction wavelength of the gain medium, ultimately causing the output power and conversion efficiency to decrease. Therefore, it is particularly important to control the spectral broadening and distortion of the seed source and adjust the center wavelength to match the gain characteristics of the solid-state gain medium.

[0003] Currently, in the spectral control process of narrow-bandwidth fiber laser, two schemes of thermoelectric cooler (TEC) temperature control tuning and thin film interference filtering are mostly used. The TEC temperature control tuning technology has the disadvantages of low temperature control tuning sensitivity, large power consumption and limited tuning range; the thin film interference filtering technology is subject to the high preparation cost and complex process of narrow-band filter, and its fixed filtering characteristics cannot be changed. Both of these two methods cannot solve the technical problem of spectral broadening and center wavelength drift of fiber seed source caused by nonlinear effects in the amplification process.

[0004] Therefore, there is an urgent need for a method that can intelligently, real-time and dynamically regulate the spectral morphology and center wavelength. SUMMARY

[0005] The present application provides a narrow-bandwidth fiber laser system and a control method thereof to solve the technical problem of spectral broadening and center wavelength drift of fiber seed source caused by nonlinear effects in the amplification process.

[0006] The application provides a narrow-bandwidth fiber laser system, comprising, in sequence, a light source, a first fiber pre-amplification module, a first regulation mechanism, a second fiber pre-amplification module, a second regulation mechanism, a fiber main amplification module and a solid amplification module; the light source is configured to output laser; the first fiber pre-amplification module is configured to pre-amplify the power of the laser; the first regulation mechanism is configured to regulate the center wavelength and the spectral width of the pre-amplified laser; the second fiber pre-amplification module is configured to pre-amplify the power of the laser again; the second regulation mechanism is configured to regulate the center wavelength and the spectral width of the pre-amplified laser again; and the fiber main amplification module and the solid amplification module are both configured to amplify the power of the laser.

[0007] In some possible implementation manners, the first regulation mechanism comprises, in sequence, a first spectral regulation module and a photoelectric detector; the narrow-bandwidth fiber laser system further comprises, in sequence, a pulse selector and a fiber acousto-optic modulator; the pulse selector is connected to the photoelectric detector, and the fiber acousto-optic modulator is connected to the second fiber pre-amplification module; and the second regulation mechanism comprises a second spectral regulation module.

[0008] In some possible implementation manners, the first spectral regulation module comprises a first base, a first fiber grating and a first piezoelectric actuation module; a first end of the first fiber grating is fixed to the first base; a second end of the first fiber grating is fixed to a first moving end of the first piezoelectric actuation module; the first moving end is configured to drive the second end to move relative to the first end, so as to adjust the center wavelength of the first fiber grating; the second spectral regulation module comprises a second base, a second fiber grating and a second piezoelectric actuation module; a third end of the second fiber grating is fixed to the second base; a fourth end of the second fiber grating is fixed to a second moving end of the second piezoelectric actuation module; and the second moving end is configured to drive the fourth end to move relative to the third end, so as to adjust the center wavelength of the second fiber grating.

[0009] The narrow-bandwidth fiber laser system provided in the first aspect of the application can solve the problems of spectral broadening and center wavelength drift caused by nonlinear effects in the amplification process of a fiber seed source, and can realize intelligent, real-time and dynamic regulation of spectral morphology and center wavelength, so as to output high-efficiency narrow-bandwidth laser.

[0010] The control method of the narrow-bandwidth fiber laser system provided in the second aspect of the application comprises: correcting a first initial voltage of a first piezoelectric actuation module in a first regulation mechanism to obtain a first corrected voltage; driving the first piezoelectric actuation module with the first corrected voltage to adjust the spectral morphology of the laser; correcting a second initial voltage of a second piezoelectric actuation module in a second regulation mechanism to obtain a second corrected voltage; driving the second piezoelectric actuation module with the second corrected voltage to adjust the spectral morphology of the laser; establishing a data set based on the second corrected voltage; the input set of the data set comprises: an input current of the fiber main amplification module and a driving voltage of the second piezoelectric actuation module; the driving voltage of the second piezoelectric actuation module is modulated within a second voltage search range, and the second voltage search range is determined based on the second corrected voltage; the output set of the data set comprises: a third power, a first spectral width and a second power, the third power being the power of the laser after passing through the solid amplification module, the first spectral width being the spectral width of the laser before passing through the solid amplification module, and the second power being the power of the laser before passing through the fiber main amplification module; training a nonlinear mapping model with the data set; the input of the nonlinear mapping model comprises a nonlinear function, the nonlinear function being established based on the input set, and the output of the nonlinear mapping model comprises the output set; optimizing the nonlinear function with a Bayesian algorithm to determine the maximum output power of the narrow-bandwidth fiber laser system; and controlling the fiber laser system based on the maximum output power.

[0011] In some possible implementation manners, the first initial voltage of the first piezoelectric actuation module in the first regulation mechanism is corrected to obtain the first corrected voltage, comprising: obtaining a first wavelength variation; the first wavelength variation is an average wavelength variation of the first fiber grating under a unit voltage in the first regulation mechanism; and the first initial voltage is determined based on the first wavelength variation.

[0012] In some possible implementation manners, the first wavelength variation is obtained by: obtaining a first driving voltage data set; the first driving voltage data set is a set of first driving voltages of the first piezoelectric actuation module collected at intervals of a preset time; determining a first driving voltage variation based on the first driving voltage data set; the first driving voltage variation is a difference between any two adjacent first driving voltages in the first driving voltage data set; obtaining a first center wavelength data set; the first center wavelength data set is a set of center wavelengths generated by the first fiber grating under a plurality of driving voltages in the first driving voltage data set, and the first driving voltage data set corresponds to the first center wavelength data set; and determining the first wavelength variation based on the first driving voltage variation and the first center wavelength data set.

[0013] In some possible implementation manners, determining the first initial voltage based on the first wavelength variation includes: obtaining a first initial wavelength; the first initial wavelength is a center wavelength of the first fiber grating under a condition without a driving voltage; determining the first initial voltage of the first piezoelectric actuator module based on a second center wavelength, the first wavelength variation, the first driving voltage variation and the first initial wavelength; the second center wavelength is a center wavelength of the laser after passing through the first fiber pre-amplification module.

[0014] In some possible implementation manners, the first initial voltage of the first piezoelectric actuator module in the first regulating mechanism is corrected to obtain a first corrected voltage, and the method further includes: determining a first preset step length based on the first driving voltage variation; determining a first voltage search range based on the first initial voltage; applying a driving voltage to the first piezoelectric actuator module at intervals of the first preset step length in the first voltage search range to obtain a first power set; determining a first power; the first power is a maximum power in the first power set; determining the first corrected voltage based on the first power; the first corrected voltage is a driving voltage corresponding to the first power.

[0015] In some possible implementation manners, the data set is established based on the second corrected voltage, and the method further includes: collecting training data; performing standardization processing on the training data; the standardization processing includes: an average value of 0 and a standard deviation of 1; establishing the data set based on the training data after the standardization processing.

[0016] In some possible implementation manners, the non-linear function is optimized by using the Bayesian algorithm, and before the maximum output power of the narrow-bandwidth fiber laser system is determined, the control method further includes: determining a plurality of constraint functions based on the first spectral width and the second power; the plurality of constraint functions are different.

[0017] The control method of the narrow-bandwidth fiber laser provided in the second aspect of the application drives the change of the refractive index and the period of the fiber Bragg grating by regulating the voltage of the piezoelectric actuator module, and then adjusts the center wavelength change, cooperates with the one-dimensional exhaustive search method, takes the optimal power output as the target, corrects the driving voltage of the piezoelectric actuator module, constructs and trains the non-linear mapping model, optimizes the objective function based on the Bayesian algorithm, and efficiently extracts the best matching center wavelength and spectral width, solves the technical problem of the spectral broadening and the center wavelength drift caused by the non-linear effect of the fiber seed source in the amplification process, and realizes the generation of high-efficiency narrow-band laser in the solid traveling wave amplifier. BRIEF DESCRIPTION OF DRAWINGS

[0018] In order to more clearly illustrate the technical solutions of the application, the drawings needed in the embodiments will be briefly introduced below. Obviously, other drawings can also be obtained by those skilled in the art without creative labor.

[0019] Figure 1 is a structural schematic diagram of a narrow-bandwidth fiber laser system provided by an embodiment of the present application;

[0020] Figure 2 is a structural schematic diagram of a first spectrum regulation module and a second spectrum regulation module provided by an embodiment of the present application;

[0021] Figure 3 is a schematic diagram of a light path of laser in a first fiber circulator provided by an embodiment of the present application;

[0022] Figure 4 is a flowchart of a control method of a narrow-bandwidth fiber laser system provided by an embodiment of the present application;

[0023] Figure 5 is a flowchart of a control method of a narrow-bandwidth fiber laser system in a specific implementation provided by an embodiment of the present application.

[0024] Illustration mark:

[0025] 1 - light source; 2 - first fiber isolator; 3 - first spectrum detection component; 4 - first fiber pre-amplification module; 5 - second fiber isolator; 6 - second spectrum detection component; 7 - first fiber circulator; 71 - first port; 72 - second port; 73 - third port;

[0026] 8 - first spectrum regulation module; 81 - first substrate; 82 - first fiber grating; 821 - first grating area; 83 - first piezoelectric actuation module; 831 - first ceramic layer; 832 - first electrode layer;

[0027] 9 - first processing unit; 10 - photodetector; 11 - pulse selector; 12 - third fiber isolator; 13 - third spectrum detection component; 14 - first power detection component; 15 - fiber acousto-optic modulator; 16 - second fiber pre-amplification module; 17 - fourth fiber isolator; 18 - fourth spectrum detection component; 19 - second fiber circulator;

[0028] 20 - second spectrum regulation module; 201 - second substrate; 202 - second fiber grating; 2021 - second grating area; 203 - second piezoelectric actuation module; 2031 - second ceramic layer; 2032 - second electrode layer;

[0029] 21 - second processing unit; 22 - residual light collector assembly; 23 - fifth fiber isolator; 24 - fifth spectral detection assembly; 25 - second power detection assembly; 26 - fiber master amplification module; 27 - fiber collimator; 28 - filtering assembly; 29 - spatial light isolator; 30 - first light splitting assembly; 31 - sixth spectral detection assembly; 32 - solid amplification module; 33 - second light splitting assembly; 34 - third power detection assembly; 35 - window mirror assembly; 36 - third processing unit; 37 - master control module. DETAILED DESCRIPTION

[0030] The technical solutions in the embodiments of the present application will be clearly described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are some but not all of the embodiments of the present application. Based on the embodiments of the present application, other embodiments obtained by those of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0031] Hereinafter, the terms "first", "second", and the like are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined with "first", "second", and the like can explicitly or implicitly include one or more features. In the description of the present application, unless otherwise specified, the meaning of "a plurality of" is two or more.

[0032] In addition, in the present application, the orientation terms such as "upper", "lower", "inner", "outer", and the like are defined with respect to the orientation of the components shown in the drawings. It should be understood that these directional terms are relative concepts, which are used for relative description and clarification, and can be changed accordingly according to the change of the orientation of the components placed in the drawings.

[0033] Narrow bandwidth fiber laser is one of the core components of modern photon technology. It compresses the spectral width of laser to an extremely narrow degree through special technology, thereby obtaining high coherence and low phase noise that ordinary laser is difficult to achieve, so as to be applied in various technical fields such as high-precision measurement, advanced sensing and next-generation communication.

[0034] Controlling the spectral broadening and distortion of the seed source and adjusting the center wavelength to match the gain characteristics of the solid gain medium plays a key role in the use of narrow bandwidth fiber laser. The reason why the output fiber seed source spectrum needs to be controlled within a narrow range is mainly that the absorption spectrum width of the gain medium (such as crystal) used in the solid traveling wave amplifier is usually only 0.5 nm~0.6 nm. If the spectral width of the seed source is too large, the spectral components beyond the range will not be effectively absorbed, and the overall extraction efficiency will be significantly reduced.

[0035] ​Currently, in the field of spectral modulation, existing technologies mainly employ two schemes: TEC (thermal control) tuning and thin-film interference filtering. In the TEC tuning method, the wavelength tuning sensitivity of the grating is relatively low, typically only about 10 pm / ℃. Therefore, to achieve wavelength adjustments on the order of 1 nm, the TEC must generate a significant temperature difference of up to 100℃. This huge temperature difference requirement directly triggers two interrelated negative effects: first, according to the laws of thermodynamics, maintaining a huge temperature difference inevitably requires the temperature control system to consume extremely high drive power; second, when the operating temperature of the TEC differs greatly from the ambient temperature, condensation inevitably occurs on the surface of the optical components, seriously threatening the long-term reliability and stability of the laser. Thin-film interference filtering technology is limited by the high manufacturing cost and complex process of narrowband filters, and its fixed filtering characteristics cannot be changed. In other words, neither method can solve the technical problems of spectral broadening and center wavelength drift caused by nonlinear effects during the amplification process of the fiber seed source.

[0036] To address the aforementioned technical issues, this application provides a narrow-bandwidth fiber laser system that effectively suppresses spectral broadening during amplification, actively compresses and shapes the output spectrum into the desired narrow-bandwidth, approximately Gaussian distribution, compensates for center wavelength drift caused by factors such as SPM and temperature, ensuring precise matching of the laser wavelength to the peak gain wavelength of the gain medium, and ultimately intelligently, in real-time, stably, and dynamically controls the spectral shape and center wavelength to efficiently generate narrow-band fiber lasers with optimal power and spectrum as the goal.

[0037] Figure 1 This is a schematic diagram of a narrow bandwidth fiber laser system provided in an embodiment of this application.

[0038] See Figure 1 As shown, the narrow-bandwidth fiber laser system provided in this application embodiment includes a light source 1, a first fiber pre-amplification module 4, a first control mechanism A1, a second fiber pre-amplification module 16, a second control mechanism A2, a fiber main amplification module 26, and a solid-state amplification module 32 arranged sequentially.

[0039] Specifically, light source 1 is configured to output laser light, enabling the laser output of the subsequent narrow-bandwidth fiber laser system.

[0040] In one feasible implementation, the light source 1 can be an optical fiber oscillator, which can generate a stable, high-quality pulsed laser with a pulse width of 8ps~12ps, a spectral width of 0.1nm~0.15nm, a repetition frequency of 20MHz, and an energy of 0.2nJ~0.3nJ.

[0041] The laser pulse energy generated by the light source 1 is too low, and if direct main power amplification is performed, the signal-to-noise ratio may be deteriorated. Therefore, the energy needs to be first increased through a pre-amplification stage to meet the requirements of subsequent main power amplification. Therefore, the first fiber pre-amplification module 4 is arranged on the light path of the laser, and the first fiber pre-amplification module 4 receives the laser and pre-amplifies the energy of the laser.

[0042] In some possible implementations, the energy of the laser after passing through the first fiber pre-amplification module 4 can be 2nJ-3nJ, the pulse width can be 8ps-12ps, the spectral width can be 0.4nm-0.5nm, and the repetition frequency can be 20MHz.

[0043] The first regulation mechanism A1 is configured to receive the laser emitted by the first fiber pre-amplification module 4, and the first regulation mechanism A1 is configured to regulate the center wavelength and the spectral width of the pre-amplified laser. After the laser passes through the first fiber pre-amplification module 4, the peak power of the laser is pre-amplified to a high level in the gain medium, thereby causing strong nonlinear optical effects, especially dominated by SPM. The SPM effect causes a series of changes in the output spectrum, such as spectral broadening, center wavelength shift, and multi-peak spectral morphology. Therefore, the first regulation mechanism A1 is arranged to shape and regulate the distorted spectrum, so as to ensure that the final output has excellent spectral morphology, narrow band, and high power.

[0044] The second fiber pre-amplification module 16 is configured to receive the laser regulated by the first regulation mechanism A1 and pre-amplify the power of the laser again.

[0045] In one specific implementation, the first fiber pre-amplification module 4 can be the same as the second fiber pre-amplification module 16. After the laser enters the second fiber pre-amplification module 16, the energy can be amplified to 5nJ-6nJ, the pulse width can be 8ps-12ps, the spectral width can be 0.5nm-0.6nm, and the repetition frequency can be 1MHz.

[0046] The second regulation mechanism A2 is configured to receive the laser pre-amplified again, and the second regulation mechanism A2 has the same effect as the first regulation mechanism A1 and can regulate the center wavelength and the spectral width.

[0047] The fiber main amplification module 26 is configured to receive the laser regulated again and realize main amplification of the output power by adjusting the current size.

[0048] The solid amplification module 32 and the fiber main amplification module 26 cooperate to realize laser output with high repetition frequency, high average power, and extremely high single-pulse energy.

[0049] The narrow-bandwidth fiber laser system provided by the embodiments of the present application can effectively suppress spectral broadening in the amplification process, actively compress and shape the output spectrum into a narrow-bandwidth, approximately Gaussian distribution form, compensate for the central wavelength drift caused by SPM and temperature and other factors, and ensure that the laser wavelength accurately matches the peak gain wavelength of the gain medium. The narrow-bandwidth laser output is finally generated stably and efficiently with the power and spectrum optimized as the target.

[0050] In some possible implementation manners, continuing to refer to Figure 1 As shown in the figure, the first regulation mechanism A1 includes a first spectrum regulation module 8 and a photoelectric detector 10, and the narrow-bandwidth fiber laser system can further include a pulse selector 11 and a fiber acousto-optic modulator 15; wherein the fiber acousto-optic modulator 15 is connected with a second fiber pre-amplification module 16.

[0051] The first spectrum regulation module 8 is configured to receive the pre-amplified laser and regulate the central wavelength and spectral width of the laser to meet the use requirements.

[0052] The input end of the photoelectric detector 10 is connected with the output end of the first spectrum regulation module 8, and the photoelectric detector 10 is configured to convert the optical signal into an electrical signal. The photoelectric detector 10 is electrically connected with the pulse selector 11 through a radio frequency line, and the pulse selector 11 is electrically connected with the integrated fiber acousto-optic modulator 15 through a radio frequency line.

[0053] The integrated fiber acousto-optic modulator 15 includes an acousto-optic driver (not shown in the figure) inside. In the narrow-bandwidth fiber laser system, the pulse selector 11 and the fiber acousto-optic modulator 15 work together: the laser output by the fiber oscillator has a repetition frequency of MHz order. Since the frequency is too high, the peak power of the output after amplification is low, and it is difficult to apply in industrial scenarios. At this time, the output frequency needs to be reduced through pulse selection, so that the peak power after amplification can be higher, so that it can be applied in use scenarios that require high pulse peak power, such as industrial scenarios. The pulse selector 11 receives a synchronization signal through the photoelectric detector 10, and outputs a set signal to the acousto-optic driver according to the parameters set through the serial port. The acousto-optic driver controls the on-off of the integrated fiber acousto-optic modulator 15 to intercept pulses of a set frequency. The intercepted pulses can be single pulses or multiple continuous pulses. Taking single pulse and a repetition frequency of 1MHz as an example, the energy of the laser after frequency selection is about 1nJ~2nJ, the pulse width is 8ps~12ps, and the spectral width is 0.13nm~0.18nm.

[0054] After the selection of the optical fiber acousto-optic modulator 15, the pulse repetition frequency is reduced, and the pulse energy and average power are also reduced. If the main power amplification is directly performed, it will lead to the deterioration of the signal-to-noise ratio. Therefore, it is necessary to pass through the pre-amplification stage again to improve its energy to meet the needs of subsequent main power amplification. The laser led out by the optical fiber acousto-optic modulator 15 will enter the second optical fiber pre-amplification module 16 for power secondary pre-amplification.

[0055] In some possible implementation manners, continuing to refer to Figure 1 As shown in the figure, the second regulation mechanism A2 includes a second spectrum regulation module 20.

[0056] The second spectrum regulation module 20 is used for receiving the secondary pre-amplified laser and regulating the center wavelength and the spectrum width of the laser to meet the use requirements. The first spectrum regulation module 8 can be the same as the second spectrum regulation module 20.

[0057] Figure 2 FIG. 1 is a structural schematic diagram of a first spectrum regulation module and a second spectrum regulation module provided by an embodiment of the present application. Figure 2 FIG. 1 (a) is a structural schematic diagram of the first spectrum regulation module 8, Figure 2 FIG. 1 (b) is a structural schematic diagram of the second spectrum regulation module 20.

[0058] In some possible implementation manners, referring to Figure 2 As shown in FIG. 1 (a), the first spectrum regulation module 8 includes a first base 81, a first fiber grating 82 and a first piezoelectric actuation module 83. The first end G1 of the first fiber grating 82 is fixed on the first base 81. The second end G2 of the first fiber grating 82 is fixed on the first moving end Y1 of the first piezoelectric actuation module 83. The first moving end Y1 is used to drive the second end G2 to move relative to the first end G1 to adjust the center wavelength of the first fiber grating 82.

[0059] Specifically, the first piezoelectric actuation module 83 can be formed by bonding and co-firing of a first ceramic layer 831 and a first electrode layer 832. The first end G1 of the first fiber grating 82 is connected with the rigid first base 81 through ultraviolet curing glue. The first end G1 is static, and the second end G2 can be fixed on the first electrode layer 832 of the first piezoelectric actuation module 83 through ultraviolet curing glue. The first electrode layer 832 can be connected with an adjustable voltage source through positive and negative electrode leads. By regulating the voltage of the first piezoelectric actuation module 83, the stretching and contraction of the first ceramic layer 831 will directly drive the second end G2 to move, so as to change the distance between the first end G1 and the second end G2, and realize the stretching or contraction of the first fiber grating 82.

[0060] The length of the first grating area 821 of the first fiber grating 82 can be 7mm-8mm, the spectral width can be 0.15mm-0.2mm, the reflectivity is greater than or equal to 99%, and the distance between the first end G1 and the second end G2 can be 10mm-11mm under the condition that the first piezoelectric actuator module 83 is not powered. According to the following formula:

[0061] (1)

[0062] (2)

[0063] (3)

[0064] wherein, is the displacement amount of the first piezoelectric actuator module 83; is the piezoelectric coefficient of the piezoelectric ceramic sheet of the first piezoelectric actuator module 83; is the number of stacked piezoelectric ceramic sheets in the first piezoelectric actuator module 83; is the driving voltage of the first piezoelectric actuator module 83; is the axial strain received by the first fiber grating 82; is the distance between the two ends of the first fiber grating 82; is the wavelength change amount of the first fiber grating 82; is the initial center wavelength of the first fiber grating 82.

[0065] The first piezoelectric actuator module 83 with model PSt150 / 3.5x3.5 / 20H is taken as an example for introduction, the size of the first piezoelectric actuator module 83 can be 3.6(high)x3.6(width)x18(length)mm, =+635pm / V, =180, =150V, =10mm, =1064nm, by calculation, =1.41nm, under the condition of 150V voltage driving, the first piezoelectric actuator module 83 can make the center wavelength of the first fiber grating 82 tune 1.41nm, to meet the use requirements.

[0066] In the prior art, the optical fiber is directly pasted on the two electrode layers of lead zirconate titanate (PZT), which limits the wavelength tuning range, and the tuning range is usually about 0.78nm, which cannot meet the use requirements in many fields. In the first piezoelectric actuator module 83 provided by the embodiment of the application, the first end G1 of the first fiber grating 82 is fixed on the rigid first substrate 81, and the second end G2 is pasted on the first electrode layer 832, which can change the axial strain The size of the sensor can expand the tuning range to 2nm~3nm.

[0067] According to the formula , The effective refractive index of the fiber core in the first fiber grating 82. The period of the first fiber grating 82 is defined as follows: During the application of tension to the first fiber grating 82, the grating spacing of the first fiber grating 82 can be controlled to increase, thus defining the period of the first fiber grating 82. As the fiber's size increases, according to the photoelastic effect of optical fibers, when the material is stretched longitudinally, its transverse dimension shrinks due to the Poisson effect. This shrinkage in transverse dimensions and the change in internal stress affect the effective refractive index of the optical fiber. Reduced. For standard quartz fiber, the grating period... The increase in is the dominant factor, and its effect far exceeds that of the effective refractive index. To reduce the impact, its center wavelength will shift towards longer wavelengths, resulting in a redshift. Conversely, if a compressive force is applied to the first fiber grating 82, it will cause the periodicity to decrease. Decrease and A slight increase in length will eventually shift the center wavelength towards shorter wavelengths, resulting in a blue shift. The change in length of the first fiber grating 82 is on the order of a tiny number and can be achieved by stretching or shrinking it.

[0068] The laser beam after passing through the second fiber pre-amplification module 16 will accumulate to a high level in the gain medium, thereby inducing strong nonlinear optical effects, such as SPM. By setting the second spectral control module 20 to shape and control the distorted spectrum, the final output can be ensured to have key characteristics such as excellent spectral morphology, narrow band and high power.

[0069] Among some feasible implementation methods, see Figure 2 As shown in (b), the second spectral modulation module 20 includes: a second substrate 201, a second fiber optic grating 202, and a second piezoelectric actuation module 203; the third end G3 of the second fiber optic grating 202 is fixed to the second substrate 201; the fourth end G4 of the second fiber optic grating 202 is fixed to the second moving end Y2 of the second piezoelectric actuation module 203; the second moving end Y2 is configured to drive the fourth end G4 to move relative to the third end G3 to adjust the center wavelength of the second fiber optic grating 202.

[0070] Specifically, the structure of the second piezoelectric actuation module 203 can be the same as that of the first piezoelectric actuation module 83. The second piezoelectric actuation module 203 can be formed by co-firing the second ceramic layer 2031 and the second electrode layer 2032. The third end G3 of the second fiber grating 202, which is stationary, can be connected to the rigid second substrate 201 through ultraviolet curing glue, and the fourth end G4 can be fixed to the second electrode layer 2032 of the second piezoelectric actuation module 203 through ultraviolet curing glue. The second electrode layer 2032 is connected to the adjustable voltage source through positive and negative lead wires. By adjusting the voltage of the second piezoelectric actuation module 203, the expansion and contraction of the second ceramic layer 2031 will directly drive the movement of the fourth end G4, thereby changing the distance between the third end G3 and the fourth end G4, and achieving the stretching or contraction of the second fiber grating 202.

[0071] In some possible implementation manners, the second fiber grating 202 can have a second grating area 2021 with a length of 2 mm to 3 mm, a reflection spectrum bandwidth of 0.27 mm to 0.32 mm, and a reflectivity of ≥99%. In the absence of voltage applied to the second piezoelectric actuation module 203, the distance between the third end G3 and the fourth end G4 is 5 mm to 6 mm. The size of the second piezoelectric actuation module 203 can be 3.6 (high) x 3.6 (wide) x 18 (long) mm. The second electrode layer 2032 is connected to the adjustable voltage source through positive and negative lead wires. By adjusting the voltage of the second piezoelectric actuation module 203, the expansion and contraction of the second ceramic layer 2031 will directly drive the movement of the fourth end G4, thereby changing the distance between the third end G3 and the fourth end G4, and achieving the stretching or contraction of the second fiber grating 202.

[0072] Specifically, the numerical calculation method is the same as that of the first fiber grating 82. In the second piezoelectric actuation module 203, = 5 mm, and the calculation can obtain = 2.82 nm. Under the condition of a voltage drive of 150 V, the second piezoelectric actuation module 203 can tune the center wavelength of the second fiber grating 202 by 2.82 nm to meet the use requirements.

[0073] In some possible implementation manners, continuing to refer to Figure 1 The narrow-bandwidth fiber laser system can further include a first fiber isolator 2, a first spectrum detection assembly 3, and a second fiber isolator 5. The first control mechanism A1 includes a second spectrum detection assembly 6, a first fiber ring 7, and a third fiber isolator 12.

[0074] Specifically, the input end of the first optical fiber isolator 2 is connected with the output end of the light source 1, and the output end of the first optical fiber isolator 2 is connected with the first optical fiber pre-amplification module 4 and the first optical spectrum detection assembly 3 respectively. The laser generated by the light source 1 enters the first optical fiber isolator 2, which can prevent the return light from damaging the light source 1, and 1% of the laser in the first optical fiber isolator 2 enters the first optical spectrum detection assembly 3, and the spectral center wavelength and the spectral width of the laser are detected through the first optical spectrum detection assembly 3.

[0075] The input end of the second optical fiber isolator 5 is connected with the output end of the first optical fiber pre-amplification module 4, and the output end of the second optical fiber isolator 5 is connected with the second optical spectrum detection assembly 6 and the first optical fiber circulator 7 respectively.

[0076] Specifically, the laser enters the second optical fiber isolator 5, which prevents the return light from damaging the devices in the first optical fiber pre-amplification module 4, and 1% of the laser in the second optical fiber isolator 5 is detected through the second optical spectrum detection assembly 6 to detect the spectral center wavelength and the spectral width after pre-amplification, so as to control the center wavelength and the spectral width in real time.

[0077] Figure 3 is a first optical fiber isolator in the laser optical path schematic diagram provided by the embodiment of the application. Figure 3 (a) in the first optical fiber isolator structure schematic diagram is shown; Figure 3 (b) and Figure 3 (c) in the first optical fiber isolator optical path schematic diagram is shown.

[0078] In some possible implementation manners, referring to Figure 3 (a) is shown, the first optical fiber circulator 7 includes a first port 71, a second port 72 and a third port 73. The laser does not interfere between the first port 71, the second port 72 and the third port 73.

[0079] Specifically, the first port 71 is connected with the second optical fiber isolator 5, and the second port 72 is connected with the first optical spectrum detection assembly 3. After the laser passes through the second optical fiber isolator 5, it enters the first optical fiber circulator 7 through the first port 71, and enters the first optical spectrum control module 8 through the second port 72, and the optical path of the laser is as shown in Figure 3 (b) is shown. The laser passing through the first optical spectrum control module 8 is divided into two parts. One part of the laser is reflected by the fiber grating and enters the third optical fiber isolator 12 through the third port 73 after passing through the first optical fiber circulator 7, which prevents the return light from damaging the devices in the front module, and the optical path of the laser is as shown in Figure 3 (c) is shown. The other part of the laser transmits through the fiber grating, the fiber grating is loss welded with a passive optical fiber, and then the laser transmitting through the fiber grating enters the photodetector 10 after attenuation.

[0080] The narrow bandwidth fiber laser system further comprises a third spectrum detection component 13, a first power detection component 14, and a first processing unit 9.

[0081] Specifically, the output end of the third fiber isolator 12 is connected with the third spectrum detection component 13, the first power detection component 14, and the fiber acousto-optic modulator 15 respectively. The third fiber isolator 12 divides 1% of the laser input to the third spectrum detection component 13, and detects the regulated spectral center wavelength and spectral width through the third spectrum detection component 13. The third fiber isolator 12 divides another 1% of the laser, and tests the regulated power through the first power detection component 14. The energy after the spectrum regulation is 1.4nJ~2.4nJ, the pulse width is 8ps~12ps, the spectral width is 0.15nm~0.2nm, and the repetition frequency is 20MHz.

[0082] The first processing unit 9 is connected with the second spectrum detection component 6, the first spectrum regulation module 8, the third spectrum detection component 13, and the first power detection component 14 respectively, and is used for receiving the parameters detected by each component.

[0083] In some possible implementation manners, the first processing unit 9 can comprise a first data acquisition module, a first data processing module, a first voltage control module, and a first communication module (not shown in the figure). The first voltage control module receives a command sent by the first communication module, and sends the command to the first piezoelectric actuation module 83. The first piezoelectric actuation module 83 receives the command to stretch or contract, drives the first fiber grating 82 to stretch or contract, and thus regulates the spectral center wavelength. The first data acquisition module acquires the spectral center wavelength and spectral width data tested by the second spectrum detection component 6, the spectral center wavelength and spectral width data tested by the third spectrum detection component 13, and the power data tested by the first power detection component 14 in real time.

[0084] Specifically, the first data acquisition module acquires a plurality of groups of data. The first group of data in the plurality of groups of data is a vector A1=[ , , , , , ]; wherein, is the voltage of the first voltage control module in the first group of data, and are the center wavelength and the spectral width tested by the second spectrum detection component 6 in the first group of data, and are the center wavelength and the spectral width tested by the third spectrum detection component 13 in the first group of data, is the power tested by the first power detection component 14 in the first group of data.

[0085] The second set of data is vector A2=[ , , , , ];......;The nth set of data is vector A n =[ , , , , , ]. The first data processing module analyzes and processes the first collected data. The first communication module is used to transmit various commands.

[0086] It is worth noting that Figure 1 The connection relationship between the components shown in the figure can be distinguished by the linearity of the connection line. A solid line indicates that the two components are connected by an optical fiber, a broken line indicates that the two components are connected by an electrical wire, and a dashed line indicates that the two components are connected by a spatial light beam.

[0087] In some possible implementation manners, the second control mechanism A2 can further include a fourth optical fiber isolator 17, a fourth optical spectrum detection assembly 18, a second optical fiber circulator 19, a fifth optical fiber isolator 23, a residual light collector assembly 22, and a fifth optical spectrum detection assembly 24.

[0088] One end of the fourth optical fiber isolator 17 is connected with the second optical fiber pre-amplification module 16, and the other end is respectively connected with the fourth optical spectrum detection assembly 18 and the second optical fiber circulator 19. The fourth optical fiber isolator 17 is used to prevent the return light from damaging the devices in the second optical fiber pre-amplification module 16. The fourth optical fiber isolator 17 divides 1% of the laser into the fourth optical spectrum detection assembly 18.

[0089] The fourth optical spectrum detection assembly 18 is used to detect the center wavelength and width of the laser after the secondary pre-amplification.

[0090] The second optical fiber circulator 19 can include a fourth port (not shown in the figure), a fifth port, and a second port. The fourth port is connected with the fourth optical fiber isolator 17, the fifth port is connected with the second spectrum control module 20, and the sixth port is connected with the fifth optical fiber isolator 23.

[0091] The light beam of the laser through the second spectral regulation module 20 is divided into two parts. One part of the light beam is reflected by the fiber grating and enters the fifth fiber isolator 23 through the second fiber circulator 19. The fifth fiber isolator 23 is used to prevent the return light from damaging the devices in the previous modules. The fifth fiber isolator 23 divides 1% of the laser, and the center wavelength and the spectral width after regulation are detected by the fifth spectral detection assembly 24. The fifth fiber isolator 23 divides another 1% of the laser, and the power after regulation is tested by the second power detection assembly 25. The energy of the laser after the second spectral regulation module 20 is about 4.2~5.2nJ, the pulse width is 8~12ps, the spectral width is 0.27~0.32nm, and the repetition frequency is 1MHz. The other part of the remaining laser beam in the second spectral regulation module 20 is guided into the remaining light collector assembly 22 through the fiber grating, so as to avoid scattering the light to other optical elements.

[0092] In some possible implementation manners, the narrow-bandwidth fiber laser system can further include a second power detection assembly 25 and a second processing unit 21.

[0093] The second power detection assembly 25 is connected with the fifth fiber isolator 23, and is used to detect the power of the laser after the secondary pre-amplification. The second processing unit 21 is connected with the first processing unit 9, the fourth spectral detection assembly 18, the fifth spectral detection assembly 24, the second spectral regulation module 20 and the second power detection assembly 25 respectively, and is used to perform data transmission with the first processing unit 9, the fourth spectral detection assembly 18, the fifth spectral detection assembly 24, the second spectral regulation module 20 and the second power detection assembly 25.

[0094] Specifically, the second processing unit 21 includes a second data acquisition module, a second data processing module, a second voltage control module and a second communication module (not shown in the figure). The second data acquisition module acquires the voltage data of the first voltage control module in the first processing unit 9, the voltage data of the second voltage control module in the second processing unit 21, the spectral center wavelength and the spectral width data tested by the fourth spectral detection assembly 18, the spectral center wavelength and the spectral width data tested by the fifth spectral detection assembly 24, and the power data tested by the second power detection assembly 25 in real time.

[0095] Specifically, the second data acquisition module acquires multiple groups of data. In the multiple groups of acquired data, the first group of data is a vector B1=[ , , , , , , ]; wherein, and respectively the voltage of the first voltage control module and the second voltage control module in the first group of data, and respectively the center wavelength and the spectral width tested by the fourth spectral detection component 18, and respectively the center wavelength and the spectral width tested by the fifth spectral detection component 24, the power tested by the second power detection component 25.

[0096] The second group of data collected is vector B2=[ , , , , , , ];......;The nth group of data collected is vector B n =[ , , , , , , ]. The second data processing module analyzes and processes the collected data. The second voltage control module receives the command sent by the second communication module and sends the command to the second piezoelectric actuator module 203, and the second piezoelectric actuator module 203 receives the command to stretch or contract, driving the second fiber grating 202 to stretch or contract, thereby realizing the adjustment of the spectral center wavelength. The second communication module is used for transmitting various commands.

[0097] In some possible implementation manners, the narrow-bandwidth fiber laser system can further include a fiber collimator 27, a filter component 28, a spatial light isolator 29, a first light splitting component 30, a sixth spectral detection component 31, a solid amplification module 32, a second light splitting component 33, a third power detection component 34, a main control module 37, and a window mirror component 35.

[0098] The fiber collimator 27 is arranged between the fiber main amplification module 26 and the filter component 28. After the laser is output by the fiber main amplification module 26, the laser is output through the fiber collimator 27 to collimate the laser, and the single-pulse energy of the laser is 10 nJ-12 nJ, the pulse width is 8 ps-12 ps, the spectral width is 0.5 nm-0.6 nm, and the repetition frequency is 1 MHz.

[0099] The filter component 28 is arranged between the fiber collimator 27 and the spatial light isolator 29. By arranging the filter component 28, stray light other than the required waveband in the laser can be filtered out to ensure spectral purity.

[0100] The spatial light isolator 29 is arranged between the filtering assembly 28 and the first light splitting assembly 30. By arranging the spatial light isolator 29, the reflected light in the laser can be inhibited to prevent damage to the front-stage device.

[0101] The first light splitting assembly 30 is arranged between the spatial light isolator 29, the solid amplification module 32 and the sixth spectrum detection assembly 31, and forms two light paths with different directions between the spatial light isolator 29, the solid amplification module 32 and the sixth spectrum detection assembly 31. Specifically, after the laser passes through the first light splitting assembly 30, about 1% of the laser is introduced into the sixth spectrum detection assembly 31 to monitor the central wavelength and the spectrum width in real time; the remaining most part (about 99%) of the laser enters the solid amplification module 32 for power amplification.

[0102] The narrow-bandwidth fiber laser system can further include a third processing unit 36. The other end of the sixth spectrum detection assembly 31 is connected to the third processing unit 36, and the third processing unit 36 can also be used to receive the data detected by the sixth spectrum detection assembly 31.

[0103] After the laser passes through the solid amplification module 32, the laser power is increased to 10W-12W, the pulse width is substantially unchanged to 8ps-12ps, and the repetition frequency is 1MHz.

[0104] The second light splitting assembly 33 is arranged between the solid amplification module 32, the third power detection assembly 34 and the window mirror assembly 35, and forms two light paths with different directions between the solid amplification module 32, the third power detection assembly 34 and the window mirror assembly 35. Specifically, the amplified light beam passes through the second light splitting assembly 33 again, and 1% of the laser is split off and sent into the third power detection assembly 34 for output power detection. The other end of the third power detection assembly 34 is connected to the third processing unit 36, and the third processing unit 36 can also be used to receive the data detected by the third power detection assembly 34.

[0105] Most of the laser in the second light splitting assembly 33 is output through a window mirror assembly 35. The window mirror assembly 35 can be a transparent optical interface, and its core role is to ensure that the optical signal passes through without interference, while physically isolating the internal precise optical elements of the system from the external complex environment, playing a key protection role.

[0106] In one specific implementation, the third processing unit 36 can include a third data acquisition module, a third data processing module, a third current adjustment module and a third communication module (not shown in the figure). The third data acquisition module acquires in real time voltage data of the second voltage control module in the second processing unit 21, current data of the pump source in the main control module 37, spectral center wavelength and spectral width data tested by the sixth spectral detection assembly 31, power data tested by the second power detection assembly 25 and power data tested by the third power detection assembly 34.

[0107] Specifically, the third data acquisition module acquires a plurality of groups of data, in which the first group of data is a vector C1=[ , , , , ]; wherein, is the voltage of the second voltage control module, is the current of the pump source in the main control module 37, and are the center wavelength and the spectral width tested by the sixth spectral detection assembly 31, respectively, is the power data tested by the second power detection assembly 25, is the power data tested by the third power detection assembly 34.

[0108] The second group of data is a vector C2=[ , , , , , ]; and the nth group of data is a vector Cn=[ n , , , , , ]. The third data processing module analyzes and processes the acquired data. The current adjustment module receives a command sent by the communication module and sends the command to the main control module 37, and the main control module 37 receives the command to adjust the current size of the pump source, thereby realizing the adjustment of the output power of the main control module 37. The third communication module is used for transmitting various commands.

[0109] ​The main control module 37 is connected with the first processing unit 9, the second processing unit 21 and the third processing unit 36 respectively. The main control module 37 comprises a power management module, a reset module, a clock module, a storage module, a central processing unit and a communication module. The communication module of the main control module 37 can transmit various commands to the first processing unit 9, the second processing unit 21 and the third processing unit 36 respectively, so as to realize real-time control of the first processing unit 9, the second processing unit 21 and the third processing unit 36.

[0110] Corresponding to the foregoing embodiments of the narrow-bandwidth fiber laser system, the application further provides embodiments of a control method of the narrow-bandwidth fiber laser system.

[0111] Figure 4 is a flowchart of a control method of a narrow-bandwidth fiber laser system provided by the application.

[0112] Referring to Figure 4 The control method of the narrow-bandwidth fiber laser system provided by the application can comprise steps S100 to S800.

[0113] Step S100: correcting a first initial voltage of the first piezoelectric actuation module 83 in the first regulation mechanism A1 to obtain a first corrected voltage.

[0114] In this step, the purpose is to obtain the parameter of the first spectrum regulation module 8 in the first regulation mechanism A1.

[0115] In some feasible implementation manners, the step S100 can comprise the following steps S110 and S120.

[0116] Step S110: obtaining a first wavelength variation; the first wavelength variation is a wavelength average variation of the first fiber grating 82 in the first regulation mechanism A1 under a unit voltage.

[0117] In the step S110, obtaining the first wavelength variation can comprise the following steps S111 to S114.

[0118] Step S111: obtaining a first driving voltage data set; the first driving voltage data set is a set of driving voltages of the first piezoelectric actuation module 83 collected at intervals of a preset time.

[0119] Specifically, the first driving voltage set of the first piezoelectric actuation module in the first spectrum regulation assembly in the historical operation parameter is obtained wherein i = 1, 2, 3, …, n; i is the time.

[0120] Step S112: Determine the change in the first driving voltage based on the first driving voltage dataset; the change in the first driving voltage is the difference between any two adjacent first driving voltages in the first driving voltage dataset.

[0121] Specifically, First driving voltage change It can also be understood as the change in voltage per unit.

[0122] Step S113: Obtain the first center wavelength dataset.

[0123] Obtain the first center wavelength set of the first fiber grating 82 (FBG1) corresponding to the first driving voltage of the first piezoelectric actuation module 83 in the historical operating parameters. Where i = 1, 2, 3, ..., n; the first center wavelength dataset is the set of center wavelengths generated by the first fiber grating 82 under the action of multiple first driving voltages in the first driving voltage dataset, and the first driving voltage dataset corresponds to the first center wavelength dataset. For example, For the first fiber grating 82, at the first driving voltage The corresponding center wavelength.

[0124] Step S114: Determine the first wavelength change based on the first driving voltage change and the first center wavelength dataset.

[0125] According to the change in the first driving voltage and the first central wavelength set The average change in the first center wavelength of FBG1 under unit voltage conditions can be obtained by calculation, that is, the change in the first wavelength. By calculating the change in the first wavelength, the performance of the first spectral modulation module 8 can be tested and the change in the first driving voltage can be calculated before the first piezoelectric actuation module 83 is used in the narrow-bandwidth fiber laser system. The first wavelength change Determine the change in the first driving voltage. Change in wavelength The correspondence.

[0126] In some feasible implementations, step S120 may include steps S121 and S122.

[0127] Step S121: Obtain the first initial wavelength; the first initial wavelength is the center wavelength of the first fiber grating 82 under no driving voltage condition.

[0128] Without applying a driving voltage, the center wavelength of the first fiber grating 82 detected is the first initial wavelength. .

[0129] Step S122: determining the first initial voltage of the first piezoelectric actuation module 83 based on the second center wavelength, the first wavelength variation, the first driving voltage variation and the first initial wavelength; the second center wavelength is the center wavelength of the laser after passing through the first fiber pre-amplification module 4.

[0130] The first data acquisition module acquires the vector An in the spectral center wavelength and spectral width data tested by the second spectral detection assembly 6 in real time Data, according to the formula , the data processing module in the first processing unit 9 calculates and processes the acquired data to obtain the initial voltage value of the first piezoelectric actuation module 83 The communication module of the first processing unit 9 sends The command to the first voltage control module in the first processing unit 9, and the first voltage control module sends the command to the first piezoelectric actuation module 83. The first piezoelectric actuation module 83 receives the command to stretch or shrink, drives the first fiber grating 82 to stretch or shrink, realizes the preliminary adjustment of the spectral center wavelength, and obtains the preliminary spectrum after the first fiber pre-amplification module 4. The first initial voltage value Determines the strain direction of the FBG1. For example, , applying a positive voltage makes the FBG1 stretched, or , applying a negative voltage makes it shrink.

[0131] In this way, the first initial voltage of the first piezoelectric actuation module 83 is calculated , the first spectral regulation module 8 performs real-time preliminary regulation to obtain the first form spectrum after the first fiber pre-amplification module 4.

[0132] Step S130: determining the first preset step length based on the first driving voltage variation.

[0133] The first preset step length is the voltage search step length, which is half of the first driving voltage variation, that is, the first preset step length is .

[0134] Step S140: determining the first voltage search range based on the first initial voltage.

[0135] The first voltage search range is ] Q1 is the first voltage constant.

[0136] Step S150: applying driving voltage to the first piezoelectric actuation module 83 with the first preset step length as the interval in the first voltage search range to obtain a first power set.

[0137] In the first voltage search range ] with the first preset step length as The driving voltage applied to the first piezoelectric actuation module 83 is changed sequentially at intervals, and the data is collected by the first data acquisition module in the first processing unit 9. Group data. Each voltage value corresponds to a synchronous power value and a synchronous wavelength value. This voltage value is a command transmitted from the first communication module to the first piezoelectric actuation module 83. The first piezoelectric actuation module 83 executes the voltage adjustment command, causing FBG1 to stretch, thereby changing the center wavelength of the FBG1 reflection spectrum (this wavelength value is obtained by the third spectral detection component 13, i.e., vector A). n In The data, which can be obtained through the first acquisition module in the first processing unit 9, thereby changing the magnitude of the power value (this power value is obtained by the first power detection component 14, i.e., the value in vector A). The data (which can be acquired through the first data acquisition module in the first processing unit 9) is recorded and stored as a single data record. A matrix with 3 rows and 3 columns, matrix D = ;

[0138] Step S160: Determine the first power. The first power is the largest power in the first power set.

[0139] The first power set can be determined in matrix D. The first power set includes... , , The first data processing module can compare the first power set composed of the third column of matrix D to determine the maximum value, which is the first power. .

[0140] Step S170: Determine the first correction voltage based on the first power; the first correction voltage is the driving voltage corresponding to the first power.

[0141] Determine the data in the first column of matrix D. The corresponding driving voltage value of the first piezoelectric actuator module 83 is the first correction voltage. In other words, for the initial voltage value The correction is performed, and the corrected voltage is: .

[0142] Step S200: The first piezoelectric actuation module 83 is driven by the first correction voltage to adjust the spectral morphology of the laser.

[0143] In this step, the first communication module will carry the first correction voltage. the first voltage control module, the first voltage control module sends a command to the first piezoelectric actuator module 83, the first piezoelectric actuator module 83 receives the command to stretch or contract, driving the first fiber grating 82 to stretch or contract, realizing the adjustment of the first spectral center wavelength, obtaining the optimal spectrum after the first fiber pre-amplification module 4, denoted as the second form spectrum. In this way, in the first voltage search range, the maximum power value measured by the first power detection assembly 14 is used as the correction basis to correct the driving voltage data of the first piezoelectric actuator module 83, and the corrected voltage is obtained, realizing the second form spectrum after the first fiber pre-amplification module 4.

[0144] Step S300: Correcting the second initial voltage of the second piezoelectric actuator module 203 in the second regulation mechanism A2 to obtain a second corrected voltage.

[0145] In step S300, the second initial voltage is corrected, which requires first obtaining the second initial voltage. The process of obtaining the second initial voltage can be the same as that of obtaining the first initial voltage, and the process of correcting the second initial voltage can be the same as that of correcting the first initial voltage.

[0146] Specifically, the driving voltage set of the second piezoelectric actuator module 203 is obtained from the historical operation parameters , wherein i = 1, 2, 3, … n, , is the second driving voltage variation, i.e. the unit voltage variation; the second center wavelength set of the second fiber grating 202 (FBG2) corresponding to the driving voltage of the second piezoelectric actuator module 203 is obtained from the historical operation parameters , wherein i = 1, 2, 3, … n. According to the voltage set and the center wavelength set , the average variation of the center wavelength of FBG2 under the condition of unit voltage is obtained .

[0147] Since the second spectrum regulation module 20 is similar in structure to the first spectrum regulation module 8, but the specific parameters are different. Specifically, the fiber grating region length, the fiber grating reflection bandwidth, the fiber grating reflectivity, the distance between the two ends, and the tunable wavelength range under the same voltage condition are different. Therefore, the calculation process of step S300 is similar to that of step S100.

[0148] In this way, before the second piezoelectric actuator module 203 is applied to the narrow bandwidth fiber laser system, the performance of the second spectrum regulation module 20 is tested, and the second wavelength variation under the second unit voltage determining the corresponding relationship between the second driving voltage of the second piezoelectric actuation module 203 and the second center wavelength of FBG2.

[0149] obtaining the second initial wavelength and the calculated second wavelength change amount wherein, is the center wavelength of the fiber grating reflection spectrum of FBG2 under the condition of no driving voltage. The center wavelength corresponding to obtained from the second data acquisition module of the second processing unit 21 is recorded as According to the formula The second data processing module in the second processing unit 21 performs calculation and processing on the collected data to obtain the second initial voltage of the second piezoelectric actuation module 203 The second communication module of the second processing unit 21 sends the command to the second voltage control module of the second processing unit 21, and the second voltage control module sends the command to the second piezoelectric actuation module 203. The second piezoelectric actuation module 203 receives the command to stretch or shrink, drives the second fiber grating 202 to stretch or shrink, realizes the preliminary adjustment of the center wavelength of the spectrum, and obtains the preliminary spectrum after the second fiber pre-amplification module 16. The second initial voltage determines the strain direction of FBG2. The example , a positive voltage is applied to stretch FBG2; or , a negative voltage is applied to shrink it.

[0150] In this way, through theoretical numerical calculation, the initial voltage of the second piezoelectric actuation module 203 is obtained, and the second spectrum control module 20 performs preliminary control to obtain the third form spectrum after the second fiber pre-amplification module 16.

[0151] The obtained is set as the initial voltage of the second piezoelectric actuation module 203, and the second preset step size and the second voltage search range ] are set, wherein Q2 is the second voltage constant. Within the second search range ], the second driving voltage applied to the second piezoelectric actuation module 203 is changed in sequence at intervals of the second preset step size , and the second data acquisition module of the second processing unit 21 collects Group data. Each voltage value corresponds to a synchronous power value and a synchronous wavelength value, and the voltage value is the command transmitted by the communication module to the second piezoelectric actuator module 203. The second piezoelectric actuator module 203 executes the adjustment voltage command to drive the FBG2 to stretch, thereby changing the center wavelength of the FBG2 reflection spectrum (this wavelength value is obtained by the fifth spectrum detection assembly 24, that is, the vector B n data in the data obtained by the second data acquisition module of the second processing unit 21), and then changes the size of the power value (this power value is obtained by the first power detection assembly 14, that is, the vector B n data in the data obtained by the second data acquisition module of the second processing unit 21). The obtained data record is stored as a 3-column matrix E,

[0152] Matrix E= , the second data processing module compares and processes all power data in the third column of matrix E to determine the maximum value, and records this data as , finds the second piezoelectric actuator module 203 driving voltage value (the data in the first column of matrix E) corresponding to , and records this data as , and corrects the second initial voltage . The corrected voltage is the second corrected voltage . The second communication module sends command to the second voltage control module, and the second voltage control module sends the command to the second piezoelectric actuator module 203. The second piezoelectric actuator module 203 receives the command to stretch or shrink, drives the second fiber grating 202 to stretch or shrink, adjusts the center wavelength of the spectrum, and obtains the optimal spectrum after the second fiber pre-amplification module 16. It is recorded as the fourth form spectrum.

[0153] Step S400: Drive the second piezoelectric actuator module 203 with the second corrected voltage to adjust the spectrum form of the laser.

[0154] Within a certain voltage range, the maximum power value measured by the second power detection assembly 25 is used as the correction basis to correct the driving voltage data of the second piezoelectric actuator module 203, and the corrected voltage is obtained, and the fourth form spectrum after the first fiber pre-amplification module 4 is realized.

[0155] Step S500: establishing a data set based on the second correction voltage; an input set of the data set includes: the input current of the fiber main amplification module 26 and the driving voltage of the second piezoelectric actuation module 203; the driving voltage of the second piezoelectric actuation module 203 is modulated in a second voltage search range, the second voltage search range is determined based on the second correction voltage; an output set of the data set includes: the third power, the first spectral width and the second power, the third power is the power of the laser after passing through the solid amplification module 32, the first spectral width is the spectral width of the laser before passing through the solid amplification module 32; and the second power is the power of the laser before passing through the fiber main amplification module 26.

[0156] In some possible implementation manners, the step S500 can include steps S510 to S530.

[0157] Step S510: collecting a plurality of sets of historical operation data of the narrow-bandwidth fiber laser system under combinations of different modulation currents (the input current of the fiber main amplification module 26, the modulation range ) and second driving voltages (the driving voltage of the second piezoelectric actuation module 203, the modulation range ], the voltage value of the second piezoelectric actuation module 203 after correction, and Q3 is a third voltage constant) of the second piezoelectric actuation module 203, the operation data including output power Pout, first spectral width and output power , wherein, , , , , are all known constants, measured by the third power detection component 34, the first spectral width measured by the sixth spectrum detection component 31, measured by the second power detection component 25, and the parameter set as input, and the parameter set as output.

[0158] Step S520: performing standardization processing on the training data.

[0159] The input and output data are standardized to have an average value of 0 and a standard deviation of 1. Since these physical quantities have different dimensions and value ranges, it is particularly important to pre-process the data set. Through data preprocessing, the training efficiency and model accuracy can be improved.

[0160] Step S530: establishing a data set based on the training data after standardization processing.

[0161] The data set is standardized to improve the accuracy of the model. The data set can be divided into a training set and a test set. The training set can be used for data training, and the test set can be used for data testing.

[0162] Step S600: training a nonlinear mapping model using the data set; the input of the nonlinear mapping model includes a nonlinear function, the nonlinear function is established based on the input set, and the output of the nonlinear mapping model includes the output set. The nonlinear mapping model is constructed, and the model mapping relationship is represented as: wherein, is a nonlinear function, is a modeling error.

[0163] Specifically, the nonlinear mapping model includes an input layer, an output layer and two hidden layers connected with each other, each hidden layer has 128 neurons, and a ReLU activation function is used.

[0164] wherein, the input layer: x= , x is a two-dimensional column vector, which is used as the input of the nonlinear mapping model; the hidden layer adopts a two-layer structure, and the activation function uses ReLU; the output layer: y= , y is a three-dimensional column vector, which is used as the output of the neural network.

[0165] The first layer in the hidden layer, .

[0166] The second layer in the hidden layer, .

[0167] The output layer, wherein, , , is a weight matrix, , , is a bias vector.

[0168] According to the following formula and the preprocessed data for training:

[0169] wherein, is a model parameter, N is the number of training samples, is the actual measured output power of the i-th sample, is the actual measured spectral width of the i-th sample, is the actual measured second fiber grating 202 power of the i-th sample, is the model predicted output power of the i-th sample, is the model predicted spectral width of the i-th sample, is the model predicted second fiber grating 202 power of the i-th sample.

[0170] In some feasible implementations, the optimizer is AdamW, with an initial learning rate of 1.5. 10 -5 The weight decay is 1.0. 10 -5 Meanwhile, the mini-batch size is set to 32. Training is monitored using a validation set with early stopping enabled: if the validation set loss shows no improvement over 15 consecutive epochs, training is stopped and the best-performing weights on the validation set are restored. To ensure repeatability, a fixed random seed should be used and the input and output should be standardized. The nonlinear mapping model is trained until convergence. Thus, the nonlinear mapping model is trained according to... Input conditions for accurate prediction Output results.

[0171] Step S700: Use the Bayesian algorithm to optimize the nonlinear function and determine the maximum output power of the narrow bandwidth fiber laser system.

[0172] Based on the aforementioned nonlinear mapping model, the Bayesian algorithm is used to optimize problems with constraints. The Bayesian algorithm consists of three core parts: surrogate model, constraint handling, and acquisition function.

[0173] Proxy model: Modeling the objective function using a Gaussian process (GP). (Right now A Gaussian process is a nonparametric model that provides the mean and variance of the predicted values. The formula is as follows: ,in, It is a mean function, typically taking the value of a constant (e.g., the mean of the training output) or zero. It is the covariance function.

[0174] In step S700, based on the first spectral width Second power Define multiple constraint functions; the multiple constraint functions are different.

[0175] Constraint handling: Gaussian processes are also used to model each constraint function. .

[0176] First constraint function: .

[0177] Second constraint function: .

[0178] Third constraint function: .

[0179] Where, x= is a decision variable.

[0180] a first control variable boundary constraint condition, .

[0181] a second control variable boundary constraint condition, .

[0182] For each constraint condition, the probability of constraint satisfaction can be calculated by a Gaussian process model, and for each point x, the feasibility probability is defined as: wherein, is the probability of the i-th constraint satisfaction.

[0183] Acquisition function: the Constrained Expected Improvement (CEI) is used as the acquisition function, which is the product of the Expected Improvement (EI) and the feasibility probability, as follows: wherein, is the Expected Improvement, defined as: , is the best objective function value in the current known feasible sample (i.e. the current optimal value).

[0184] Table 1

[0185] ;

[0186] In one specific implementation, based on Table 1, the feasible points are x1, x4, x5, wherein the maximum value of Pout is 11.9 under x4, so the current , x4 is the optimal control variable parameter under the maximum value of Pout. Purpose: to use the Bayesian optimization algorithm to autonomously search for the optimal control variable combination to realize intelligent control of the narrow-bandwidth fiber laser system, thereby improving its extraction efficiency and optimizing the spectral shaping effect.

[0187] Step S800: control the narrow-bandwidth fiber laser system based on the maximum output power.

[0188] In this embodiment, a spectral modulation module consisting of a narrowband uniform fiber Bragg grating, a piezoelectric actuation module, and a circulator is constructed. This module shapes the split pulse spectrum after amplification, resulting in a narrower bandwidth (spectral width ≤ 0.5~0.6 nm) and an approximately Gaussian distribution. A fixing method and fixed endpoint distance are designed to match the grating. By adjusting the voltage of the piezoelectric actuation module, the refractive index and period of the fiber Bragg grating are changed, thereby adjusting the center wavelength. Using a one-dimensional exhaustive search method, with optimal power output as the objective, the driving voltage of the piezoelectric module is corrected. A nonlinear mapping model is constructed and trained. Based on a Bayesian algorithm, the objective function is optimized, and the optimal combination of control variables (modulation current) is intelligently selected. and driving voltage V PAM2 Locked solid-state gain medium ( The optimal matching center wavelength and spectral width are extracted efficiently from crystals, enabling intelligent, real-time, and dynamic control of spectral morphology and center wavelength, and realizing the generation of high-efficiency narrowband lasers in solid-state traveling wave amplifiers.

[0189] Figure 5 This is a flowchart illustrating a control method for a narrow-bandwidth fiber laser system in a specific implementation provided in this application embodiment.

[0190] In a specific implementation, see Figure 5 As shown, the control method for a narrow-bandwidth fiber laser system may include the following steps S501 to S506.

[0191] Step S501: Obtain the historical operating parameters, specifically the set of driving voltages for the first piezoelectric actuation module. and its corresponding FBG1 wavelength set The average wavelength change of FBG1 was obtained. .

[0192] Specifically, step S501 can refer to step S100.

[0193] Step S502: Obtain preset values and According to the formula The initial voltage is obtained. Set voltage search step size and voltage search range The maximum value is determined by the first power detection component. The corrected voltage is obtained. .

[0194] Specifically, step S502 can refer to step S200.

[0195] Step S503: obtaining a set of driving voltages of the second piezoelectric actuation module in historical operation and a corresponding set of FBG2 wavelengths , obtaining an average variation of the FBG2 wavelengths .

[0196] Specifically, step S503 can refer to step S300.

[0197] Step S504: obtaining a preset value and , according to the formula , obtaining an initial voltage , setting a voltage search step and a voltage search range ], determining a maximum value by the second power detection component, obtaining a corrected voltage .

[0198] Specifically, step S504 can refer to step S400.

[0199] Step S505: obtaining historical operation data of the system under different modulation currents and driving voltages , and constructing a nonlinear mapping model.

[0200] Step S506: under the multiple constraint conditions of constraint function 1: ; constraint function 2: ; constraint function 3: , performing collaborative optimization on and by the Bayesian optimization algorithm to maximize the system output power .

[0201] Specifically, step S505 and step S506 can refer to steps S500 to S800.

[0202] It should be noted that other embodiments of the application will be readily apparent to those skilled in the art from consideration of the specification and practice of the application disclosed herein. The application is intended to cover any variations, uses or adaptations of the application following, in general, the principles of the application and including such

[0203] It should be understood that the application is not limited to the precise construction that has been described above and shown in the accompanying drawings, and that various modifications and changes can be made by those skilled in the art without departing from the scope of the application. The true scope of the application is set forth in the attached claims.

Claims

1. A narrow-bandwidth fiber laser system, characterized in that, It includes a light source, a first fiber optic pre-amplification module, a first control mechanism, a second fiber optic pre-amplification module, a second control mechanism, a fiber optic main amplification module, and a solid-state amplification module arranged sequentially. The light source is configured to output laser light; The first fiber pre-amplification module is configured to pre-amplify the power of the laser; The first control mechanism is configured to control the center wavelength and spectral width of the pre-amplified laser; The second fiber pre-amplification module is configured to pre-amplify the power of the laser a second time; The second control mechanism is configured to control the center wavelength and spectral width of the laser after secondary pre-amplification; Both the fiber optic main amplification module and the solid-state amplification module are configured to amplify the power of the laser. The first control mechanism includes a first spectral control module and a photodetector arranged sequentially. The narrow-bandwidth fiber laser system further includes: a pulse selector and a fiber acousto-optic modulator arranged sequentially; the pulse selector is connected to the photodetector, and the fiber acousto-optic modulator is connected to the second fiber pre-amplification module; The second control mechanism includes a second spectral control module; The first spectral modulation module includes: a first substrate, a first fiber grating, and a first piezoelectric actuation module; a first end of the first fiber grating is fixed to the first substrate; a second end of the first fiber grating is fixed to a first movable end of the first piezoelectric actuation module; the first movable end is configured to drive the second end to move relative to the first end to adjust the center wavelength of the first fiber grating. The second spectral modulation module includes: a second substrate, a second fiber grating, and a second piezoelectric actuation module; the third end of the second fiber grating is fixed to the second substrate; the fourth end of the second fiber grating is fixed to the second movable end of the second piezoelectric actuation module; the second movable end is configured to drive the fourth end to move relative to the third end to adjust the center wavelength of the second fiber grating.

2. A control method for a narrow-bandwidth fiber laser system, characterized in that, The control method, applied to the narrow-bandwidth fiber laser system of claim 1, includes: The first initial voltage of the first piezoelectric actuation module in the first control mechanism is corrected to obtain the first corrected voltage; The first piezoelectric actuation module is driven by the first correction voltage to adjust the spectral morphology of the laser. The second initial voltage of the second piezoelectric actuation module in the second control mechanism is corrected to obtain the second corrected voltage; The second piezoelectric actuation module is driven by the second correction voltage to adjust the spectral morphology of the laser. A dataset is established based on the second correction voltage; the input set of the dataset includes: the input current of the fiber optic main amplification module and the driving voltage of the second piezoelectric amplification module; the driving voltage of the second piezoelectric amplification module is modulated within a second voltage search range, and the second voltage search range is determined based on the second correction voltage; the output set of the dataset includes: a third power, a first spectral width, and a second power, wherein the third power is the power of the laser after passing through the solid-state amplification module, the first spectral width is the spectral width of the laser before passing through the solid-state amplification module, and the second power is the power of the laser before passing through the fiber optic main amplification module; A nonlinear mapping model is trained using the dataset; the input of the nonlinear mapping model includes a nonlinear function, which is established based on the input set, and the output of the nonlinear mapping model includes the output set. The nonlinear function is optimized using a Bayesian algorithm to determine the maximum output power of the narrow-bandwidth fiber laser system. The narrow-bandwidth fiber laser system is controlled based on the maximum output power.

3. The control method for a narrow-bandwidth fiber laser system according to claim 2, characterized in that, The step of correcting the first initial voltage of the first piezoelectric actuation module in the first control mechanism to obtain the first corrected voltage includes: Obtain the first wavelength change; the first wavelength change is the average wavelength change of the first fiber grating in the first control mechanism under a unit voltage. The first initial voltage is determined based on the first wavelength change.

4. The control method for a narrow-bandwidth fiber laser system according to claim 3, characterized in that, The acquisition of the first wavelength change includes: Obtain the first driving voltage dataset; the first driving voltage dataset is a collection of the first driving voltages of the first piezoelectric actuation module collected at preset time intervals; The first driving voltage change is determined based on the first driving voltage dataset; the first driving voltage change is the difference between any two adjacent first driving voltages in the first driving voltage dataset. Obtain the first center wavelength dataset; the first center wavelength dataset is the set of center wavelengths generated by the first fiber grating under the action of multiple driving voltages in the first driving voltage dataset, and the first driving voltage dataset corresponds to the first center wavelength dataset; The first wavelength change is determined based on the first driving voltage change and the first center wavelength dataset.

5. The control method for a narrow-bandwidth fiber laser system according to claim 4, characterized in that, Determining the first initial voltage based on the first wavelength change includes: Obtain a first initial wavelength; the first initial wavelength is the center wavelength of the first fiber grating under no driving voltage condition; The first initial voltage of the first piezoelectric actuation module is determined based on the second center wavelength, the first wavelength change, the first driving voltage change, and the first initial wavelength; the second center wavelength is the center wavelength of the laser after passing through the first optical fiber pre-amplification module.

6. The control method for a narrow-bandwidth fiber laser system according to claim 5, characterized in that, The step of correcting the first initial voltage of the first piezoelectric actuation module in the first control mechanism to obtain the first corrected voltage further includes: A first preset step size is determined based on the first change in driving voltage; The first voltage search range is determined based on the first initial voltage; Within the first voltage search range, a driving voltage is applied to the first piezoelectric actuation module at intervals of the first preset step size to obtain a first power set. Determine the first power; the first power is the largest power in the first power set; A first correction voltage is determined based on the first power; the first correction voltage is a driving voltage corresponding to the first power.

7. The control method for a narrow-bandwidth fiber laser system according to claim 5, characterized in that, The process of establishing the dataset based on the second corrected voltage also includes: Collect training data; The training data is standardized; the standardization process includes setting the mean to 0 and the standard deviation to 1. A dataset is built based on the standardized training data.

8. The control method for a narrow-bandwidth fiber laser system according to claim 7, characterized in that, Before optimizing the nonlinear function using a Bayesian algorithm to determine the maximum output power of the narrow-bandwidth fiber laser system, the control method further includes: Multiple constraint functions are determined based on the first spectral width and the second power; the multiple constraint functions are different.

Images