A tunable microsecond pulse train light source for high-power microwave photon radar

Abstract

A tunable microsecond pulse train light source for high-power microwave photon radar comprises a microsecond pulse laser, a main frequency modulation module, a preamplifier, a precompensation module, a multi-stage energy amplifier, a multi-channel signal generator, a control computer and a control signal; the microsecond pulse laser, the main frequency modulation module, the preamplifier, the precompensation module and the multi-stage energy amplifier are sequentially connected in communication, and the multi-channel signal generator is respectively connected in communication with the microsecond pulse laser, the preamplifier, the precompensation module and the multi-stage energy amplifier through the control signal; the control computer is connected in communication with the multi-channel signal generator; the invention adopts a multi-stage synchronous pump structure, which can effectively suppress the generation of ASE in the process of high-power pulse train laser amplification under low repetition rate, and at the same time, by optimizing the pump pulse width and the signal delay between each stage, the light-to-light conversion efficiency caused by the low peak power of the microsecond pulse can be effectively improved to achieve high-power laser output.

Description

Technical Field

[0001] The invention relates to a tunable pulse train light source, in particular to a tunable microsecond pulse train light source for high-power microwave photon radar. Background Art

[0002] The new photoconductive microwave technology uses high-power tunable high-repetition-rate pulse train light as the light source, which is incident on a wide-bandgap photoconductive semiconductor switch (PCSS), and then amplified by bias voltage to generate tunable high-power microwaves. When using this method to generate high-power microwaves, the output power of the microwaves is affected by the peak power of the pulse train laser, and the frequency, pulse width, and main frequency of the output microwaves are all determined by the pulse light source. These advantages have made the tunable pulse train light source widely concerned by researchers in the field. Since the microwaves generated by the new photoconductive microwave technology have the characteristics of high power, high frequency (~GHz), tunability, and array synthesis, the tunable pulse train light source has great potential for application in microwave photon radar and phased array radar. In order to make the tunable pulse train laser suitable for high-power microwave photon radar applications, on the one hand, it is necessary to increase the pulse width of the pulse train laser (generally in the microsecond level) to increase the detection distance of the radar; on the other hand, the frequency of the pulse train laser needs to be tunable at a high frequency (adjustable to ~GHz) so that the radar can be tuned to a higher frequency band (>L band), thereby improving the detection accuracy and range of the radar and enabling the radar to operate in multiple modes; in addition, it is necessary to maintain the uniformity of the output pulse envelope of the output pulse train light source, thereby improving the detection sensitivity and action time of the radar.

[0003] Relevant personnel have conducted research on tunable pulse train lasers. In 2019, Case 1: The patent name is "High-energy pulse cluster laser as a signal source for photoconductive devices in microwave systems" (publication number: 201910526330.7). It reports a high-energy pulse cluster laser. The laser system has a fully polarization-maintaining narrow linewidth output. The patent specification shows that the maximum pulse width of the pulse cluster laser is 200ns. Since it uses two editable waveform signal boards to achieve compensation of the laser pulse waveform, and the editable waveform signal board requires a preset waveform, it cannot achieve real-time waveform compensation; the patent can achieve 10W peak power and 30W average power output in implementation case 1, but due to the inhibition of nonlinear benefits, the power of the pulse cluster laser is difficult to further increase. In 2023, Case 2 was published in High Power Laser Science and Engineering, Volume 11, Page 8, entitled "High-energy and high-peak-power GHz burst-mode all-fiber laser with a uniform envelope and tunable intra-burst pulses". The laser system has a pulse width of 66ns and a sub-pulse tunable range of 1-10GHz. In order to obtain high-power output, a synchronous amplification system with a 4-stage main amplifier is used to increase the power or energy to achieve an energy output of 13.3mJ. At the same time, in order to achieve a flat waveform envelope at high power, two waveform compensation modules are used. The all-fiber amplification system described in the results of the paper is limited by nonlinear effects, and the output energy cannot be further increased. In addition, since the all-fiber amplifier uses a non-full polarization-maintaining fiber system, it cannot be used as a fiber seed source to further amplify its energy using solid hybrid amplification.

[0004] From the above background cases, it can be found that the existing high-power tunable pulse train laser system is difficult to apply to the field of high-power microwave photon radar due to some parameter limitations. Specifically, 1. The pulse width of the existing pulse train light source is in the nanosecond order (less than microseconds), while the field of high-power microwave photon radar requires a high-power microsecond tunable pulse train light source in order to improve the detection distance and accuracy. 2. It is difficult for the existing pulse train light source to achieve real-time adjustment of the waveform under high-power output. Since the existing pulse train light source waveform compensation module uses a preset waveform compensation module and requires a preset waveform, it is difficult to achieve real-time waveform compensation during the amplification process and achieve rectangular waveform output. 3. The existing light source is suppressed by nonlinearity and it is difficult to increase the energy; since the hybrid amplification of optical fiber plus solid is an effective way to increase power, solid hybrid amplification requires the optical fiber seed to be a fully polarization-maintaining narrow-linewidth high-power laser laser output, and the higher the energy of the optical fiber seed, the easier it is for the solid laser to further amplify its power. In Case 1, although a fully polarization-maintaining optical fiber system was used, due to nonlinear effects, it was impossible to achieve higher power output of the optical fiber laser, which increased the difficulty of the solid hybrid amplification system. In case 2, since the system uses a non-full polarization-maintaining laser amplification system, it cannot be used as a seed source for a solid hybrid amplification system to further increase the power. Therefore, it is particularly important to invent a tunable microsecond pulse train light source for high-power microwave photon radar, with a pulse width of microseconds, real-time waveform compensation to simplify waveform compensation, and a GHz tunable pulse train light source with full polarization-maintaining narrow linewidth and high power output. Summary of the invention

[0005] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a tunable microsecond pulse train light source for high-power microwave photon radar. Microsecond pulse laser output is achieved by adopting a fully polarization-maintaining narrow-linewidth microsecond pulse train laser, and GHz pulse train laser modulation is achieved by adopting a large-bandwidth modulation module. The waveform compensation module adopts an arbitrary waveform signal generator to tune the voltage of the compensation signal in real time to compensate the waveform of the high-power pulse train laser. At the same time, a multi-stage fully polarization-maintaining synchronous pump amplifier module is used to amplify the energy of the microsecond tunable pulse train laser, and finally high-energy narrow-linewidth tunable microsecond pulse train laser output is achieved.

[0006] In order to solve the above technical problems, the technical solution proposed by the present invention is: a tunable microsecond pulse train light source for high-power microwave photon radar, comprising a microsecond pulse laser, a main frequency modulation module, a preamplifier, a precompensation module, a multi-stage energy amplifier, a multi-channel signal generator, a control computer and a control signal; the microsecond pulse laser, the main frequency modulation module, the preamplifier, the precompensation module and the multi-stage energy amplifier are sequentially connected in communication, the multi-channel signal generator is respectively connected in communication with the microsecond pulse laser, the preamplifier, the precompensation module and the multi-stage energy amplifier through the control signal; the control computer is connected in communication with the multi-channel signal generator;

[0007] The microsecond light pulses generated by the microsecond pulse laser are transformed into a tunable microsecond pulse train seed source after passing through a main frequency modulation module;

[0008] The pre-amplifier compensates for the energy loss of electro-optical modulation, so that the microsecond pulse train seed source has enough energy to provide to the waveform pre-compensation module, and the optical time domain pulse waveform after amplification by the pre-amplifier is still a quasi-rectangular waveform;

[0009] The pre-compensation module includes an acousto-optic modulator and an editable signal generator. The editable signal generator generates a telecommunication signal with a low start and a high end, which is driven by the acousto-optic modulator and transmitted to the acousto-optic modulator to edit the waveform of the optical pulse. The edited signal satisfies the equation , I output is the output pulse envelope, I input Input pulse envelope, G(t) is the real-time output gain, where G(t) satisfies , G 0 is the small signal gain, E sat is the optical fiber saturation absorption energy, G 0 and E sat Through experimental measurement, the frequency of the microsecond pulse laser can be adjusted in the range of 10-1kHz, the pulse width can be adjusted in the range of 1μs-1ms, the waveform of the pulse output is quasi-rectangular, the central wavelength of the output spectrum is 1064nm, and the line width is 0.05nm;

[0010] The multi-channel signal generator generates a digital signal to synchronously trigger the microsecond pulse laser and the acousto-optic modulation module, and simultaneously generates an analog signal with adjustable amplitude and pulse width to perform power control on the pre-amplifier and the multi-stage amplifier;

[0011] The control computer is connected to the high-precision multi-channel signal generator to realize the control of various signals of the high-precision multi-channel signal generator.

[0012] The above-mentioned tunable microsecond pulse train light source for high-power microwave photon radar, preferably, the main frequency modulation module includes an electro-optic modulator and a signal source; the input end of the electro-optic modulator is connected to the microsecond pulse laser, and the input and output optical fibers of the electro-optic modulator are consistent with the microsecond pulse laser.

[0013] The above-mentioned tunable microsecond pulse train light source for high-power microwave photon radar, preferably, the input end of the pre-amplifier is connected to the output optical fiber of the electro-optic modulator, the output power of the pre-amplifier is controlled by an analog control signal generated by a high-precision multi-channel signal generator, the average power and peak power after pre-amplification are less than the average power and peak power of the acousto-optic modulator, and the pre-amplifier transmits the amplified light to the pre-compensation module.

[0014] The above-mentioned tunable microsecond pulse train light source for high-power microwave photon radar preferably has a multi-stage energy amplifier that amplifies the pre-compensated microsecond tunable pulse train laser energy, and the microsecond tunable pulse train achieves high-energy output after passing through the multi-stage amplifier. By outputting different energy waveforms and cooperating with the pre-compensation signal of the pre-compensation module, a rectangular pulse envelope output is output at high energy.

[0015] The above-mentioned tunable microsecond pulse train light source for high-power microwave photon radar, preferably, the output end of the multi-stage amplifier has an isolator and a coated end cap to prevent the return light from damaging the laser system.

[0016] Compared with the prior art, the advantages of the present invention are:

[0017] 1. The waveform compensation module of the present invention can realize real-time compensation under high-power laser; in order to ensure flexible and convenient compensation of the rectangular envelope of the output pulse, the present invention adopts an editable arbitrary waveform generator to compensate the optical waveform of the output high-power microsecond pulse, and the output pulse waveform can be compensated in real time by changing the voltage amplitude of the output electrical signal of the editable arbitrary waveform generator, and cooperating with the AOM matching amplifier, and finally outputting a quasi-rectangular microsecond tunable microsecond pulse train laser.

[0018] 2. The present invention can realize 1-20GHz tunable pulse train laser output; the present invention uses a large bandwidth electro-optical modulator (>20GHz) to modulate the microsecond pulse laser, and transmits the high-frequency RF source signal output to the large bandwidth electro-optical modulator to achieve the tuning of the GHz large bandwidth microsecond pulse train sub-pulse laser. This makes the pulse train light source of the present invention applicable to L-Ku band radar applications

[0019] 3. The present invention can realize high-power microsecond pulse train laser output with narrow line width. The present invention adopts a fully polarization-maintaining microsecond pulse laser as the seed source of fiber amplification. The microsecond pulse laser is modulated into a GHz-tunable microsecond pulse train laser by a modulation module. In the laser amplification process, the present invention adopts a multi-stage synchronous pumping structure, which can effectively suppress the generation of ASE in the process of high-power pulse train laser amplification under low repetition rate. At the same time, by optimizing the pump pulse width and the signal delay between each stage, the light-to-light conversion efficiency problem caused by the low peak power of the microsecond pulse can be effectively improved. All devices and amplifiers of the present invention are fully polarization-maintaining structures, so that fully polarization-maintaining narrow-linewidth high-power microsecond pulse train laser output can be realized. The present invention can be used as a high-power pulse train seed source to be further amplified by solid hybrid amplification to increase energy. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The present invention is a schematic diagram of a tunable microsecond pulse train light source structure for high-power microwave photon radar.

[0021] Figure 2 It is a schematic diagram of the timing of signals generated by the high-precision multi-channel signal generator of the present invention.

[0022] Figure 3 It is the pre-compensated electrical signal generated by the arbitrary waveform generator of Example 1.

[0023] Figure 4 This is the pulse train seed laser after compensation in Example 1.

[0024] Figure 5 This is a diagram of the tunable main frequency of the microsecond pulse train light source in Example 1 between 1 and 5 GHz.

[0025] Figure 6 This is the time domain waveform of the microsecond pulse train outputted at 520uJ in Example 1.

[0026] Legend

[0027] 1. Microsecond pulse laser; 21. Electro-optic modulator, 22. Signal source; 3. Pre-amplifier; 41. Acousto-optic modulator, 42. Arbitrary waveform signal generator; 5. Multi-stage energy amplifier; 6. High-precision multi-channel signal generator; 7. Control computer; 81. Digital trigger signal, 82; Analog control signal. DETAILED DESCRIPTION

[0028] In order to facilitate the understanding of the present invention, the present invention will be described more comprehensively and carefully in combination with preferred embodiments below, but the protection scope of the present invention is not limited to the following specific embodiments.

[0029] It should be noted that when an element is described as being "fixed, fixed, connected or connected to" another element, it can be directly fixed, fixed, connected or connected to the other element, or it can be indirectly fixed, fixed, connected or connected to the other element through other intermediate connectors.

[0030] Unless otherwise defined, all the professional terms used below have the same meanings as those generally understood by those skilled in the art. The professional terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention.

[0031] Figure 1 The figure shows a schematic diagram of a tunable microsecond pulse train light source for high-power microwave photon radar of the present invention, which mainly includes a microsecond pulse laser; a microsecond pulse laser 1, a main frequency modulation module 2, a preamplifier 3, a precompensation module, a multi-stage energy amplifier 5, a high-precision multi-channel signal generator 6, a control computer 7, and a control signal. The microsecond pulse laser 1, the main frequency modulation module 2, the preamplifier 3, the precompensation module, and the multi-stage energy amplifier 5 are connected to each other; the high-precision multi-channel signal generator 6 is respectively connected to the microsecond pulse laser 1, the preamplifier 3, the precompensation module, and the multi-stage energy amplifier 5 through the control signal, and the control computer 7 is connected to the high-precision multi-channel signal generator 6.

[0032] The microsecond pulse laser 1 is a polarization-maintaining microsecond narrow linewidth laser with adjustable frequency and pulse width. Its frequency is adjustable in the range of 10-1 kHz, its pulse width is adjustable from 1μs to 1ms, the waveform of the pulse output is quasi-rectangular, the central wavelength of the output spectrum is 1064nm, and the line width is less than 0.05nm. The output power of the microsecond pulse laser 1 can be adjusted, and its maximum average power and peak power are less than the average power and peak power of the electro-optic modulator 21. The microsecond pulse laser 1 has an external trigger function, and can be synchronously triggered by a digital trigger signal 81 generated by a high-precision multi-channel signal generator 6.

[0033] The main frequency modulation module 2 includes an electro-optic modulator 21 and a signal source 22, wherein the electro-optic modulator 21 is an intensity modulator with a bandwidth of 1-20GHz. The modulator is set with a suitable bias voltage of 0~4V to ensure that the modulation degree of the modulated output sub-pulse is 100%, and the input and output optical fibers of the electro-optic modulator are consistent with the microsecond pulse laser 1. The signal source 22 can generate a 1-20GHz sinusoidal signal input to the electro-optic modulator 21. The input end of the electro-optic modulator 21 is connected to the microsecond pulse laser 1. The microsecond light pulse generated by the microsecond pulse laser 1 becomes a tunable pulse train seed source after passing through the main frequency modulation module 2. The tunable pulse train laser is sent to the pre-amplifier 3 after passing through the modulation module 2.

[0034] The preamplifier 3 is mainly used to compensate for the energy loss of the electro-optical modulation module 2, so that the pulse train seed source has enough energy to provide to the waveform pre-compensation module. The optical time domain pulse waveform after amplification by the preamplifier 3 is still a quasi-rectangular waveform. The input end of the preamplifier 3 is connected to the output optical fiber of the electro-optical modulator 21. The output power of the preamplifier 3 can be controlled by the analog control signal 82 generated by the multi-channel signal generator 6. The average power and peak power of the preamplifier 3 after amplification are less than the average power and peak power of the acousto-optic modulator 41. The preamplifier 3 transmits the amplified microsecond pulse train laser to the pre-compensation module.

[0035] The pre-compensation module includes an acousto-optic modulator 41 and an arbitrary waveform signal generator 42; the pre-compensation module mainly edits the quasi-rectangular time domain pulse waveform transmitted by the pre-amplifier 3 into a laser pulse with a low front and a high back to offset the waveform front edge convex distortion caused by the gain saturation effect of the subsequent multi-stage amplifier 5, so that the final output waveform is a quasi-rectangular. The bandwidth of the acousto-optic modulator 41 is greater than 100MHz, and the extinction ratio is greater than 20dB; the maximum storage data point of the arbitrary waveform signal generator 42 is greater than 10M, and the sampling rate is greater than 100MSa / s. The telecommunication signal generated by the arbitrary waveform signal generator 42 with a low front and a high back is driven by the acousto-optic modulator and transmitted to the acousto-optic modulator 41 to complete the waveform editing of the optical pulse. The edited signal satisfies the equation , I output is the output pulse envelope, I input Input pulse envelope, G(t) is the real-time output gain, where G(t) satisfies , G 0 is the small signal gain, E sat is the optical fiber saturation absorption energy, G 0 and E sat The arbitrary waveform signal generator 42 can adjust the amplitude of the edited compensation electrical signal, thereby performing real-time compensation for the optical waveform. The arbitrary waveform signal generator 42 can also realize an external trigger function, and can be synchronously triggered by a digital trigger signal 81 generated by a high-precision multi-channel signal generator 6.

[0036] The multi-stage amplifier 5 includes N (N>2) stages of amplification. The multi-stage amplifier 5 is a fully polarization-maintaining laser amplification system, which mainly amplifies the pre-compensated microsecond tunable pulse train laser energy. The microsecond tunable pulse train achieves high-energy output after passing through the multi-stage amplifier. By outputting different energy waveforms and cooperating with the pre-compensation signal of the pre-compensation module 3, a rectangular pulse envelope output is output under high energy. The output of the multi-stage amplifier 5 is controlled by an analog control signal 82 generated by a high-precision multi-channel signal generator 6. The output end of the multi-stage amplifier 5 is provided with an isolator and a coated end cap to prevent the return light from damaging the laser system.

[0037] The high-precision multi-channel signal generator 6 has an accuracy of less than 10ns. It can not only generate a digital signal 81 to synchronously trigger the microsecond pulse laser 1 and the acousto-optic modulation module 4, but also generate an analog signal with adjustable amplitude and pulse width to perform power control on the pre-amplifier 3 and the multi-stage amplifier 5. All signals generated by the high-precision multi-channel signal generator 6 can achieve synchronous control of the signals. Figure 2 The timing diagram of different pulse signals generated by the high-precision multi-channel signal generator 6, where 81 is a digital 3.3V trigger signal, 82 is an analog control signal, the amplitude and pulse width of which can be adjusted, and the trailing edges of all signals are aligned to achieve system synchronization, so as to achieve the effect of suppressing ASE.

[0038] The control computer 7 is connected to the high-precision multi-channel signal generator 6 , and mainly controls the various signals of the high-precision multi-channel signal generator 6 .

[0039] In order to operate the tunable microsecond pulse train light source, the specific implementation steps of the present invention are as follows.

[0040] The first step: turn on the high-precision multi-channel signal generator 6, output the trigger signal 81, adjust the analog signal 82, and connect the signal generated by the high-precision multi-channel signal generator 6 to the microsecond pulse laser 1, the pre-amplifier 3, the pre-compensation module, and the main amplifier 5.

[0041] Step 2: Adjust the output power, frequency, pulse width and other parameters of the microsecond pulse laser 1. The microsecond pulse laser 1 generates a pulse laser with low repetition rate, microsecond pulse width and narrow line width under the trigger signal 81.

[0042] Step 3: The signal source 22 in the main frequency modulation module 2 is set to output a GHz signal to the electro-optic modulator 21, and the electro-optic modulator 21 modulates the pulse laser with low repetition rate, microsecond pulse width and narrow linewidth emitted by the microsecond pulse laser 1 into a microsecond pulse train laser with adjustable main frequency.

[0043] Step 4: Adjust the analog control signal 82 from the high-precision multi-channel signal generator 6 to the pre-amplifier 3, and use the pre-amplifier 3 to amplify the microsecond pulse train laser emitted by the main frequency modulation module 2. The amplified power is less than the maximum average power and peak power of the acousto-optic modulator 41.

[0044] Step 5: Input pre-compensation data to the arbitrary waveform generator 42, which generates an amplitude-adjustable electrical waveform signal from the data and transmits it to the acousto-optic modulator 41, thereby completing the waveform compensation of the microsecond pulse train seed, and the compensated microsecond pulse train laser is output to the main amplifier 5.

[0045] Step 6: The main amplifier 5 receives the compensated microsecond pulse train laser sent by the pre-compensation, and by adjusting the analog control signal 82 given to the main amplifier 5 by the high-precision multi-channel signal generator 6, the main amplifier 5 amplifies the energy of the compensated microsecond pulse train laser received by the pre-compensation. The envelope of the amplified microsecond pulse train laser is rectangular, and the line width is less than 0.4nm. Example

[0046] The present invention is a schematic diagram of a tunable microsecond pulse train light source for high-power microwave photon radar, which mainly includes a microsecond pulse laser; a microsecond pulse laser, a main frequency modulation module, a preamplifier, a precompensation module, a multi-stage energy amplification, a high-precision and high-precision multi-channel signal generator, a control computer, and a control signal. The microsecond pulse laser, the main frequency modulation module, the preamplifier, the precompensation module, and the multi-stage energy amplifier are arranged in sequence from left to right and are interconnected; the high-precision multi-channel signal generator is connected to the microsecond pulse laser, the preamplifier, the precompensation module, and the multi-stage energy amplification through the control signal, and the control computer is connected to the high-precision multi-channel signal generator.

[0047] The microsecond pulse laser is a polarization-maintaining microsecond narrow linewidth laser with adjustable frequency and pulse width. Its frequency is adjustable in the range of 10-1kHz, the pulse width is adjustable from 1μs to 1ms, the waveform of the pulse output is quasi-rectangular, the center wavelength of the output spectrum is 1064nm, and the line width is 0.05nm. The output power of the microsecond pulse laser can be adjusted to output the maximum average power and peak power less than the average power and peak power of the electro-optic modulator. The microsecond pulse laser has an external trigger function, and synchronous triggering is achieved through the digital trigger signal generated by a high-precision and high-precision multi-channel signal generator.

[0048] The main frequency modulation module includes an electro-optic modulator and a signal source. The electro-optic modulator is an intensity modulator with a bandwidth of 10GHz. The bias voltage of the modulator is set to about 4V to ensure that the modulation output of the sub-pulse is 100%. The input and output optical fibers of the electro-optic modulator are consistent with the microsecond pulse laser. The arbitrary waveform generator can generate a 1-5GHz sinusoidal signal input to the electro-optic modulator. The input end of the electro-optic modulator is connected to the microsecond pulse laser. The microsecond optical pulses generated by the microsecond pulse laser become a tunable microsecond pulse train seed source after passing through the main frequency modulation module.

[0049] The pre-amplifier compensates for the energy loss of electro-optical modulation so that the microsecond pulse train seed source has enough energy to provide to the waveform pre-compensation module. The optical time domain pulse waveform after amplification by the pre-amplifier is still a quasi-rectangular waveform. The pre-amplifier input end is connected to the output optical fiber of the electro-optic modulator. The output power of the pre-amplifier is controlled by an analog control signal generated by a high-precision multi-channel signal generator. The average power and peak power after pre-amplification are less than the average power and peak power of the acousto-optic modulator. The pre-amplifier transmits the amplified light to the pre-compensation module.

[0050] The pre-compensation module includes an acousto-optic modulator and an editable signal generator; the pre-compensation module edits the quasi-rectangular time domain pulse waveform transmitted by the pre-amplification into a laser pulse with a low front and a high back to offset the waveform front convex distortion caused by the gain saturation effect of the subsequent multi-stage amplification, so that the final output waveform is quasi-rectangular. The bandwidth of the acousto-optic modulator is 200MHz, and the extinction ratio is 20dB; the editable signal generator generates a telecommunication signal with a low front and a high back, which is driven by the acousto-optic modulator and transmitted to the acousto-optic modulator to complete the waveform editing of the optical pulse. The edited signal satisfies the equation , I output is the output pulse envelope, I input Input pulse envelope, G(t) is the real-time output gain, where G(t) satisfies , G 0 is the small signal gain, E sat is the optical fiber saturation absorption energy, G 0 and E sat It can be measured experimentally. The editable signal generator can adjust the amplitude of the edited compensation electrical signal, thereby performing real-time compensation for the optical waveform. The editable signal generator can realize the external trigger function, and can be synchronously triggered by the digital trigger signal generated by the high-precision and high-precision multi-channel signal generator.

[0051] The multi-stage amplifier 5 includes three stages of amplification. The multi-stage amplifier is a fully polarization-maintaining laser amplification system, which mainly amplifies the pre-compensated microsecond tunable pulse train laser energy. The microsecond tunable pulse train achieves high-energy output after passing through the multi-stage amplifier. By outputting different energy waveforms and cooperating with the pre-compensation signal of the pre-compensation module, a rectangular pulse envelope output is maintained at high energy. The output of the multi-stage amplifier is controlled by an analog control signal generated by a high-precision multi-channel signal generator. The output end of the multi-stage amplifier is provided with an isolator and a coated end cap to prevent the return light from damaging the laser system.

[0052] The high-precision multi-channel signal generator has an accuracy of 1ns. It can not only generate digital signals to synchronously trigger the microsecond pulse laser and the acousto-optic modulation module, but also generate analog signals with adjustable amplitude and pulse width to control the power of the pre-amplifier and multi-stage amplifier. All signals generated by the high-precision multi-channel signal generator can achieve synchronous control of the signals. Figure 2 The timing diagram of different pulse signals generated by the high-precision multi-channel signal generator, where 81 is a 3.3V digital trigger signal, 82 is an analog control signal, the amplitude and pulse width of which can be adjusted, and the trailing edges of all signals are aligned to achieve system synchronization, so as to achieve the effect of suppressing ASE.

[0053] The control computer is connected to the high-precision multi-channel signal generator to realize the control of various signals of the high-precision multi-channel signal generator.

[0054] To enable the operation of this system, the specific implementation steps of the present invention are as follows.

[0055] The first step: turn on the high-precision multi-channel signal generator, and connect the signal generated by the high-precision multi-channel signal generator to the microsecond pulse laser, the pre-amplifier, the pre-compensation module, and the main amplifier.

[0056] Step 2: Adjust the output power, frequency, pulse width and other parameters of the microsecond pulse laser. The microsecond pulse laser generates a rectangular pulse laser with a frequency of 10 Hz, a pulse width of 5.5 μs, and a narrow linewidth of 0.04 nm.

[0057] Step 3: The signal generator in the main frequency modulation module is set to output a 1GHz signal to the electro-optical modulator. The modulator modulates the pulse laser with low repetition rate, microsecond pulse width and narrow linewidth emitted by the microsecond pulse laser into a microsecond pulse train laser with adjustable main frequency.

[0058] Step 4: Adjust the analog control signal from the high-precision multi-channel signal generator to the pre-amplifier, and use the pre-amplifier to amplify the microsecond pulse train laser emitted by the main frequency modulation module. The amplified power is less than the maximum average power and peak power of the acousto-optic modulator.

[0059] Step 5: Input pre-compensation data to the editable arbitrary waveform generator, which will generate an electrical waveform with adjustable amplitude. Figure 3 As shown in the figure, the horizontal axis is time, the unit is μs, and the vertical axis is the voltage of the electrical signal, the unit is V. The voltage amplitude of the electrical signal generated by the arbitrary waveform generator is about 1V. The editable electrical signal is transmitted to the acousto-optic modulator and the waveform compensation of the microsecond pulse train seed is completed. The compensated microsecond pulse train laser is output to the main amplifier. Figure 4 To compensate for the subsequent burst seed laser, it can be seen that the rising edge of the microsecond burst seed waveform has been trimmed to offset the gain saturation effect of the subsequent main amplifier.

[0060] Step 6: The main amplifier receives the compensated microsecond pulse train laser sent by the pre-compensation, and by adjusting the analog control signal sent by the high-precision multi-channel signal generator to the main amplifier, the main amplifier is used to amplify the energy of the compensated microsecond pulse train laser received by the pre-compensation. The envelope of the amplified microsecond pulse train laser is rectangular, and the line width is less than 0.4nm.

[0061] Figure 6 The adjustable range of the sub-pulse frequency of the pulse train seed of the present invention can be found by setting the frequency of the arbitrary waveform generator to 1-5 GHz, such as Figure 5 As shown, the horizontal axis is the frequency, the unit is GHz, and the vertical axis is the signal strength, the unit is dBm. This embodiment can achieve tunable sub-pulse frequency of 1-5 GHz. Figure 6 For the case of the present invention, when the main frequency of the sub-pulse is set to 1 GHz, the main amplifier outputs a time domain waveform at an energy of 520 uJ. It can be found that the waveform output is quasi-rectangular, with a half-height width of 6 μs and a top width of 5 μs.

[0062] The advantages of this embodiment are: 1. This embodiment uses an editable arbitrary waveform generator to compensate for the optical waveform of the microsecond pulse. The editable arbitrary waveform generator can change the voltage amplitude of the input and output electrical signals in real time. By using the AOM to cooperate with the output waveform of the amplifier for real-time compensation, a quasi-rectangular microsecond tunable microsecond pulse train laser can be output.

[0063] 2. This embodiment uses a narrow-linewidth microsecond pulse laser with a wavelength of 1064nm and adjustable frequency and pulse width as the seed source of the light source to achieve narrow-linewidth microsecond pulse seed laser output, and uses a wide-bandwidth electro-optical modulator to achieve wide-bandwidth tuning of GHz microsecond pulse string sub-pulses.

[0064] 3. This embodiment adopts a multi-stage synchronous pumping structure, which can effectively suppress the generation of ASE during high-power pulse train laser amplification at low repetition rate. At the same time, by optimizing the pump pulse width and the signal delay between each stage, the light-to-light conversion efficiency caused by the low peak power of microsecond pulses can be effectively improved to achieve high-power laser output.

Claims

1. A tunable microsecond pulse train light source for high-power microwave photon radar, characterized in that: It includes a microsecond pulse laser, a main frequency modulation module, a preamplifier, a precompensation module, a multi-stage energy amplifier, a multi-channel signal generator, a control computer and a control signal; the microsecond pulse laser, the main frequency modulation module, the preamplifier, the precompensation module and the multi-stage energy amplifier are sequentially connected in communication, and the multi-channel signal generator is respectively connected in communication with the microsecond pulse laser, the preamplifier, the precompensation module and the multi-stage energy amplifier through the control signal; the control computer is connected in communication with the multi-channel signal generator; The microsecond light pulses generated by the microsecond pulse laser are transformed into a tunable microsecond pulse train seed source after passing through a main frequency modulation module; The pre-amplifier compensates for the energy loss of electro-optical modulation, so that the microsecond pulse train seed source has enough energy to provide to the waveform pre-compensation module, and the optical time domain pulse waveform after amplification by the pre-amplifier is still a quasi-rectangular waveform; The pre-compensation module includes an acousto-optic modulator and an editable signal generator. The editable signal generator generates a telecommunication signal with a low start and a high end, which is driven by the acousto-optic modulator and transmitted to the acousto-optic modulator to edit the waveform of the optical pulse. The edited signal satisfies the equation , I output is the output pulse envelope, I input Input pulse envelope, G(t) is the real-time output gain, where G(t) satisfies , G 0 is the small signal gain, E sat is the optical fiber saturation absorption energy, G 0 and E sat Through experimental measurement, the frequency of the microsecond pulse laser can be adjusted in the range of 10-1kHz, the pulse width can be adjusted in the range of 1μs-1ms, the waveform of the pulse output is quasi-rectangular, the central wavelength of the output spectrum is 1064nm, and the line width is 0.05nm; The multi-channel signal generator generates a digital signal to synchronously trigger the microsecond pulse laser and the acousto-optic modulation module, and simultaneously generates an analog signal with adjustable amplitude and pulse width to perform power control on the pre-amplifier and the multi-stage amplifier; The control computer is connected to the high-precision multi-channel signal generator to realize the control of various signals of the high-precision multi-channel signal generator.

2. The tunable microsecond pulse train light source for high-power microwave photon radar according to claim 1, characterized in that: The main frequency modulation module includes an electro-optical modulator and a signal source; The input end of the electro-optic modulator is connected to the microsecond pulse laser, and the input and output optical fibers of the electro-optic modulator are consistent with the microsecond pulse laser.

3. The tunable microsecond pulse train light source for high-power microwave photon radar according to claim 1, characterized in that: The input end of the preamplifier is connected to the output optical fiber of the electro-optic modulator, the output power of the preamplifier is controlled by an analog control signal generated by a high-precision multi-channel signal generator, the average power and peak power after preamplification are less than the average power and peak power of the acousto-optic modulator, and the preamplifier transmits the amplified light to the pre-compensation module.

4. The tunable microsecond pulse train light source for high-power microwave photon radar according to claim 1, characterized in that: The multi-stage energy amplifier amplifies the pre-compensated microsecond tunable pulse train laser energy. The microsecond tunable pulse train achieves high energy output after passing through the multi-stage amplifier. By outputting different energy waveforms and coordinating with the pre-compensation signal of the pre-compensation module, a rectangular pulse envelope output is maintained at high energy.

5. The tunable microsecond pulse train light source for high-power microwave photon radar according to claim 4, characterized in that: The output end of the multi-stage amplifier is provided with an isolator and a coated end cap to prevent the return light from damaging the laser system.

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