A laser system with controllable pulse states and a control method thereof

Abstract

The application relates to the field of laser technology and provides a laser system with controllable pulse states and a control method thereof. The control method of the laser system with controllable pulse states comprises the following steps: when the cavity length of an FP cavity is in an initial matching state and the air pressure in the FP cavity is a standard air pressure, a pump light source is controlled to adjust the pump power in a first set; in response to a target pulse interval being smaller than an initial pulse interval, the pump light source is controlled to keep the target power unchanged, the air pressure of the FP cavity is adjusted in a preset range, and the cavity length of the FP cavity is adjusted in a second set; a target cavity length is determined; the laser is controlled to output in a first pulse state; and the laser is controlled to output in a second pulse state. The control method introduces controllable abnormal wave forms with high peak power as physical layer disturbances or random sections according to a predetermined frame structure, improves the reliability and safety of system signal transmission without affecting data section transmission.

Description

Technical Field

[0001] This application relates to the field of laser technology, and in particular to a laser system with controllable pulse state and its control method. Background Technology

[0002] Lasers, as a carrier of data transmission, have advantages such as high bandwidth, low loss, and resistance to electromagnetic interference, and are widely used in fields such as fiber optic communication, precision measurement, and medical equipment.

[0003] In existing data transmission methods, high-speed data transmission is mainly achieved through single solitons or dissipative solitons in lasers. Current physical layer security schemes typically employ noise injection, random phase modulation, or continuous chaotic lasers to scramble the signal, or to mask the signal or generate keys. However, these encryption methods often involve "end-to-end scrambling," reducing the signal-to-noise ratio and potentially raising the bit error rate threshold for legitimate receivers. This places high demands on receiver performance and impacts communication reliability. Summary of the Invention

[0004] This application provides a pulse-state controllable laser system and its control method, which can ensure communication reliability while enhancing physical layer security.

[0005] The control method for a pulse-state controllable laser system provided in the first aspect of this application includes: when the cavity length of the FP cavity is in its initial fit state and the gas pressure inside the FP cavity is at a standard gas pressure, controlling the pump source to adjust the pump power using a first set; the first set is a set of multiple powers formed with the initial power as the initial value and a first step size as the step value; in response to a target pulse spacing being less than the initial pulse spacing, controlling the pump source to maintain the target power unchanged, introducing regulating gas into the FP cavity to adjust the gas pressure of the FP cavity within a preset range, and adjusting the cavity length of the FP cavity using a second set; the initial pulse spacing is the pulse spacing corresponding to the initial power, and the second set is a set of multiple cavity lengths formed with the initial fit state as the initial value and a second step size as the step value; the initial pulse spacing is... The pulse interval corresponding to the laser output in the first pulse state, the first pulse state including the dissipative soliton molecule state of the laser; determining the target cavity length; the target cavity length is the cavity length of the FP cavity corresponding to the target peak power being greater than twice the peak power in the first pulse state; the target peak power is obtained by converting the voltage signal received and output by the first high-speed photodetector; the target cavity length is the cavity length of the FP cavity corresponding to the laser output in the second pulse state; the second pulse state includes the abnormal wave state of the laser; controlling the real-time pump power of the pump source to be the target power and the real-time cavity length of the FP cavity to be the initial bonding state, the laser outputs in the first pulse state; controlling the real-time pump power of the pump source to be the target power and the real-time cavity length of the FP cavity to be the target cavity length, the laser outputs in the second pulse state.

[0006] In some feasible implementations, in response to the target pulse spacing being less than the initial pulse spacing, the following methods are employed: using a time-stepping method, the pulse state of the laser is determined by combining the nonlinear Schrödinger equation with the cavity length, refractive index, and target power of the FP cavity; wherein the refractive index of the FP cavity is obtained by adjusting the gas pressure of the FP cavity; in response to the laser outputting in a first pulse state, the target pulse spacing corresponding to the first pulse state is obtained; the target pulse spacing is obtained by converting the voltage signal output by the first high-speed photodetector after receiving the laser.

[0007] In some feasible implementation methods, determining the target cavity length includes: determining the target cavity length by using a time-stepping method, utilizing the nonlinear Schrödinger equation in combination with the cavity length, refractive index, and target power of the FP cavity to determine the pulse state of the laser; in response to the laser outputting in a second pulse state, determining the target cavity length corresponding to the second pulse state; wherein, when the laser outputs in the second pulse state, the target peak power is greater than twice the peak power in the first pulse state.

[0008] In some feasible implementations, the refractive index within the FP cavity is the same in the first and second pulse states of the laser.

[0009] In some feasible implementations, the control method for a pulse-state controllable laser system also includes: controlling the real-time pump power of the pump source to be less than the target power, and outputting the laser in a third pulse state; the third pulse state includes the dissipative soliton state.

[0010] The control method for a pulse-state controllable laser system provided in this application introduces a controllably generated anomalous wave morphology with high peak power as a physical layer disturbance or random segment according to a predetermined frame structure. This improves the reliability and security of signal transmission of the pulse-state controllable laser system without affecting data segment transmission. It can stably output multiple soliton molecules, with high signal-to-noise ratio and distinguishability, reducing the performance requirements of the licensed receiver and achieving stable and reliable data demodulation at the receiver.

[0011] The second aspect of this application provides a pulse-state controllable laser system, comprising: a pump source configured to generate laser light; an adjustment module connected to the pump source at its input end, the adjustment module having an annular cavity in which the laser light propagates in a preset direction; the adjustment module including a high-speed adjustable interference component; the high-speed adjustable interference component including a fixed FP cavity fiber and a movable FP cavity fiber disposed opposite to each other, the movable FP cavity fiber being movable relative to the fixed FP cavity fiber to form an FP cavity between the fixed FP cavity fiber and the movable FP cavity fiber; and an FPGA microcontroller connected to the adjustment module, the FPGA microcontroller being configured to control the adjustment module to switch the pulse state of the laser light based on the pump power of the pump source and the cavity length of the FP cavity; the pulse state including a first pulse state and a second pulse state.

[0012] In some feasible implementations, the high-speed adjustable interference component also includes a base, a moving part, and a gas source; the moving part is disposed on the base; the fixed fiber of the FP cavity is fixed on the base, and the movable fiber of the FP cavity is disposed on the moving part. The moving part is configured to drive the movable fiber of the FP cavity to move closer to or further away from the fixed fiber of the FP cavity in order to adjust the cavity length of the FP cavity; the gas source is connected to the FP cavity and is configured to introduce regulating gas into the FP cavity to adjust the gas pressure of the FP cavity.

[0013] In some feasible implementations, the fixed fiber of the FP cavity includes a first end face, and the movable fiber of the FP cavity includes a second end face, with the first end face and the second end face disposed opposite to each other; the first end face is coated with a first reflective film, and the second end face is coated with a second reflective film, wherein both the first reflective film and the second reflective film include a multilayer dielectric film structure.

[0014] In some feasible implementations, the adjustment module further includes a polarization-maintaining wavelength division multiplexer, a polarization-maintaining circulator, and a first coupler arranged sequentially along a preset direction; the polarization-maintaining wavelength division multiplexer is configured to guide the laser into the ring cavity; the pulse-state controllable laser system also includes a saturable absorber and a polarization-maintaining fiber; the first port of the polarization-maintaining circulator is located in the output optical path of the polarization-maintaining wavelength division multiplexer, and the second port of the polarization-maintaining circulator is sequentially connected to the saturable absorber and the polarization-maintaining fiber; the third port of the polarization-maintaining circulator is connected to a high-speed tunable interferometer component; the first coupler is located between the high-speed tunable interferometer component and the polarization-maintaining wavelength division multiplexer, and the first coupler is configured to transmit the laser output from the high-speed tunable interferometer component back to the polarization-maintaining wavelength division multiplexer, and the first coupler is also configured to output the laser.

[0015] In some feasible implementations, the adjustment module further includes polarization-maintaining erbium-doped gain fiber, polarization-maintaining filter, polarization-maintaining isolator, and polarization-maintaining dispersion compensation fiber; the polarization-maintaining erbium-doped gain fiber and polarization-maintaining filter are arranged sequentially between the polarization-maintaining wavelength division multiplexer and the polarization-maintaining circulator according to a preset direction; the polarization-maintaining isolator is arranged between the polarization-maintaining circulator and the high-speed adjustable interference component; the polarization-maintaining dispersion compensation fiber is arranged between the first coupler and the polarization-maintaining wavelength division multiplexer; the pulse-state controllable laser system also includes a second coupler and a first high-speed photodetector, which are arranged sequentially between the adjustment module and the FPGA microcontroller.

[0016] The pulse-state controllable laser system provided in the second aspect of this application adopts the control method of the pulse-state controllable laser system provided in the first aspect. Therefore, its beneficial technical effects can be found in the first aspect, and will not be repeated here. Attached Figure Description

[0017] To more clearly illustrate the technical solution of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of the structure of a laser system with controllable pulse state provided in an embodiment of this application;

[0019] Figure 2 This is a schematic diagram of the structure of a high-speed adjustable interference component provided in an embodiment of this application;

[0020] Figure 3 This is a schematic diagram of the control flow of the electronic control part in an FPGA microcontroller provided in an embodiment of this application;

[0021] Figure 4 This is a schematic flowchart of a control method for a pulse-state controllable laser system provided in an embodiment of this application;

[0022] Figure 5 This is a comparative analysis diagram of an FP cavity before and after stretching, provided in an embodiment of this application;

[0023] Figure 6 This is a schematic diagram of three pulse states of a laser provided in an embodiment of this application;

[0024] Figure 7 This is a flowchart illustrating a control method for a pulse-state controllable laser system, as provided in a specific implementation of this application.

[0025] Illustration markings:

[0026] 1. Pump light source; 2. Adjustment module;

[0027] 21. High-speed adjustable interference component; 211. FP cavity fixed fiber; 211a. First end face; 212. FP cavity movable fiber; 212a. Second end face; 213. FP cavity; 214. Base; 215. Movable component; 216. Air source; 216a. Air inlet channel; 217. First fixing component; 218. Sleeve; 219. First control valve; 220. Second control valve; 221. Second fixing component; 222. Third fixing component;

[0028] 22. Polarization-maintaining wavelength division multiplexer; 23. Polarization-maintaining circulator; 24. First coupler; 25. Polarization-maintaining erbium-doped gain fiber; 26. Polarization-maintaining filter; 27. Polarization-maintaining isolator; 28. Polarization-maintaining dispersion compensation fiber;

[0029] 3. FPGA microcontroller; 4. Saturable absorber; 5. Polarization-maintaining fiber; 6. Second coupler; 7. First high-speed photodetector; 8. Second photodetector. Detailed Implementation

[0030] The technical solutions of the embodiments of this application will be clearly described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. Other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are all within the protection scope of this application.

[0031] In the following description, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this application, unless otherwise stated, "a plurality of" means two or more.

[0032] Furthermore, in this application, directional terms such as "upper," "lower," "inner," and "outer" are defined relative to the indicated placement of the components in the accompanying drawings. It should be understood that these directional terms are relative concepts, used for relative description and clarification, and can change accordingly depending on the placement of the components in the accompanying drawings.

[0033] Lasers, as a carrier of data transmission, have advantages such as high bandwidth, low loss, and resistance to electromagnetic interference, and are widely used in fields such as fiber optic communication, precision measurement, and medical equipment.

[0034] During signal transmission, controllable peak power is introduced according to a predetermined frame structure. The predetermined frame structure refers to the agreed-upon time framing and intra-frame segmentation rules between the transmitting and licensed receivers. This clarifies the optical output state type corresponding to different time segments, thereby confining anomalous wave morphologies within specific frame segments as physical layer scrambling or random segments, improving the security of the optical communication system. The licensed receiver is one that shares the predetermined frame structure and signal decision rules with the transmitting end, enabling stable demodulation of soliton molecular states when the data segment location is known. The unlicensed receiver, lacking the pre-shared parameters, cannot correctly distinguish between data segments and anomalous wave scrambling segments, and under random high peak power, interferes with and degrades the receiver's detection performance. Within the data segment, soliton molecular states exhibit stable and predictable peak power characteristics, allowing for the determination of data symbols based on the presence or absence of peak power. For example, a light pulse with a predetermined peak power can represent data "1", while a light-free situation without peak power can represent data "0", thus achieving data transmission with a high signal-to-noise ratio and easy identification by licensed receivers. However, anomalous wave morphologies are characterized by randomly occurring high peak power, and their amplitude and timing are unpredictable. They can strongly interfere with the decision threshold, synchronization circuit, and detector operation of unlicensed receivers, and may even lead to degradation or failure of their receiving performance. By confining the above-mentioned disturbance process within a controllable anomalous waveband, the data segment always maintains a stable soliton molecular state output.

[0035] Stable dissipative soliton molecules can effectively improve information capacity and transmission speed, and possess high controllability and coherence, making them essential in fundamental applications and cutting-edge fields such as optical storage and optical communication. Current data transmission methods primarily achieve high-speed data transmission through single solitons or dissipative soliton molecules. Existing physical layer security schemes typically employ noise injection, random phase modulation, or continuous chaotic lasers for signal masking or key generation. However, noise injection and continuous chaotic laser masking are often "end-to-end" scrambling methods, reducing the signal-to-noise ratio and potentially raising the bit error rate threshold at legitimate receivers, while also placing high demands on receiver performance.

[0036] To address the aforementioned technical problems, this application provides a control method for a pulse-state controllable laser system. The method involves placing a FP cavity structure within the annular cavity of the pulse-state controllable laser system. After the pump power in the pump source is increased to the point of soliton generation, the anomalous wave is generated by adjusting the cavity length and the pressure of the argon gas within the FP cavity. Furthermore, the method allows for controllable switching between soliton molecules and the anomalous wave, outputting the anomalous wave and dissipative soliton molecules according to a predetermined frame structure.

[0037] Figure 1 This is a schematic diagram of the structure of a pulse-state controllable laser system provided in an embodiment of this application.

[0038] See Figure 1 As shown, the pulse-state controllable laser system provided in this application embodiment may include a pump source 1, an adjustment module 2, and an FPGA microcontroller 3.

[0039] Pump source 1 is used to generate laser light. Pump source 1 can be a polarization-maintaining butterfly pump source with an output wavelength of 980 nm. The polarization-maintaining butterfly pump source 1 outputs polarization-maintaining pump light, which helps ensure the axial coupling stability between erbium-doped fibers and reduces polarization-dependent coupling fluctuations. Its purpose is to provide pump light for the erbium-doped gain fiber, thereby generating a 1550 nm signal light.

[0040] Specifically, the pump light source 1 can be driven by the FPGA microcontroller 3.

[0041] The input end of the adjustment module 2 is connected to the pump light source 1. The adjustment module 2 is provided with an annular cavity, in which the laser is transmitted in a preset direction. The adjustment module 2 includes a high-speed adjustable interference component 21. The high-speed adjustable interference component 21 includes a fixed FP cavity fiber 211 and a movable FP cavity fiber 212 arranged opposite to each other. The movable FP cavity fiber 212 can move relative to the fixed FP cavity fiber 211 to form an FP cavity 213 (Fabry-Pérot cavity) between the fixed FP cavity fiber 211 and the movable FP cavity fiber 212. In this way, by precisely controlling the displacement of the movable FP cavity fiber 212, the equivalent cavity length in the FP cavity 213 can be dynamically adjusted.

[0042] The FPGA microcontroller 3 is connected to the adjustment module 2. The FPGA microcontroller 3 is used to control the adjustment module 2 to switch the pulse state of the laser based on the pump power of the pump source 1 and the cavity length of the FP cavity 213. The pulse state includes a first pulse state and a second pulse state. The first pulse state includes the dissipative soliton molecule state of the laser, and the second pulse state includes the abnormal wave state of the laser.

[0043] In this way, by cooperating with the FPGA microcontroller 3 and the adjustment module 2, the two pulse states of dissipative soliton molecules and anomalous waves can be switched at will, so as to achieve secure coding with high signal-to-noise ratio and low bit error rate reception in the same system.

[0044] In some feasible implementations, the FPGA microcontroller 3 can be an FPGA (Field-Programmable Gate Array) + MCU (microcontroller unit), such as a microcontroller with data processing capabilities combined with an FPGA.

[0045] Figure 2This is a schematic diagram of the structure of a high-speed adjustable interference component provided in an embodiment of this application; wherein, Figure 2 Image (a) shows a schematic diagram of the high-speed adjustable interference component 21. Figure 2 Figure (b) shows a partial schematic diagram of the FP cavity 213 in the high-speed adjustable interference component 21.

[0046] See Figure 2 As shown in (a), the high-speed adjustable interference component 21 also includes a base 214, a moving part 215 and an air source 216.

[0047] Specifically, the fixed fiber 211 of the FP cavity is fixed to the base 214 by the first fixing member 217. The movable fiber 212 of the FP cavity is movably disposed on the base 214 by the moving member 215. The moving member 215 can drive the movable fiber 212 of the FP cavity to move closer to or away from the fixed fiber 211 of the FP cavity, so as to adjust the cavity length of the FP cavity 213. For example, when the moving member 215 drives the movable fiber 212 of the FP cavity away from the fixed fiber 211 of the FP cavity, the distance between the fixed fiber 211 and the movable fiber 212 of the FP cavity increases, and the cavity length of the FP cavity 213 increases. For example, when the moving member 215 drives the movable fiber 212 of the FP cavity closer to the fixed fiber 211 of the FP cavity, the distance between the fixed fiber 211 and the movable fiber 212 of the FP cavity decreases, and the cavity length of the FP cavity 213 decreases.

[0048] In some feasible implementations, the movable component 215 can be connected to the drive end of a driving device (not shown in the figure), which is disposed within the base 214. The driving device can be a stepper motor, whose output can drive the movable component 215 to translate in a moving or rotating manner to control the length of the FP cavity 213.

[0049] The gas source 216 is connected to the FP cavity 213. The gas source 216 can be used to introduce regulating gas into the FP cavity 213 to regulate the gas pressure of the FP cavity 213.

[0050] See also the following for some feasible implementation methods. Figure 2 As shown in (a), the air source 216 can be a cylinder assembly, which can realize real-time and precise control of the air pressure in the FP chamber 213. Among them, the FPGA microcontroller 3 is used to control the movement of the moving part 215 and the pressure adjustment operation of the air source 216.

[0051] See Figure 2 As shown in (b), the high-speed adjustable interference component 21 may also include a sleeve 218, which is sleeved on the ends of the FP cavity fixed fiber 211 and the FP cavity movable fiber 212 to precisely constrain the relative position and coaxiality of the two fiber end faces and form an FP cavity 213 between the two fiber ends.

[0052] Specifically, both ends of the sleeve 218 are fixed to the base 214 by the second fixing member 221 and the third fixing member 222, respectively. Among them, the first fixing member 217, the second fixing member 221 and the third fixing member 222 can be fixing members of the same height to ensure that the FP cavity 213 is set horizontally, and can also effectively prevent the moving member 215 from affecting the stability of the FP cavity 213 during operation.

[0053] See also Figure 2 As shown in (b), the high-speed adjustable interference component 21 may further include a first control valve 219 and a second control valve 220. The FP chamber 213 is connected to the air intake channel 216a of the air source 216 through the first control valve 219, and the FP chamber 213 is connected to the external environment through the second control valve 220. The first control valve 219 and the second control valve 220 are used to independently control the inlet and outlet rates and directions of the gas in the FP chamber 213. The first control valve 219 can be a miniature proportional valve and integrates a pressure sensor. The second control valve 220 can be an electromagnetic vent valve, which is connected to allow air to enter.

[0054] See also Figure 2 As shown in (b), the FP cavity fixed fiber 211 includes a first end face 211a, and the FP cavity movable fiber 212 includes a second end face 212a. The first end face 211a and the second end face 212a are disposed opposite to each other. The first end face 211a is coated with a first reflective film, and the second end face 212a is coated with a second reflective film. Both the first reflective film and the second reflective film include a multilayer dielectric film structure. Both the FP cavity fixed fiber 211 and the FP cavity movable fiber 212 can be polarization-maintaining single-mode fibers, with the FP cavity fixed fiber 211 being the incident end and the FP cavity movable fiber 212 being the output end.

[0055] Specifically, the first and second reflective films can have identical structures, with reflectivities of (50–90) ± 1%. They are formed by alternating stacks of high-refractive-index oxides and low-refractive-index silicon dioxide, and are prepared using ion beam sputtering to achieve dense, low-absorption, and low-scattering properties. To reduce residual stress in the thin film and suppress thermally induced drift, the first and second reflective films employ stress-compensating structures and can be symmetrically coated on both sides of the substrate to counteract warping stress, with an absolute value not exceeding 30 MPa. After coating, further annealing and pre-aging treatments are performed to release stress and stabilize spectral characteristics, ensuring stable reflectivity and phase conditions under high-temperature and high-power operating conditions, and enabling repeatable switching between mode-locked and extreme event states. Meanwhile, the first and second reflective films exhibit polarization-independent characteristics. The angle variation between the first end face 211a and the second end face 212a remains at 0±0.1°, and the polarization dependence |Rs-Rp| < 0.5% (the difference in reflectivity between the two polarization directions is essentially zero; Rs is the reflectivity for S-polarized light in the S direction, and Rp is the reflectivity for p-polarized light in the P direction). The laser damage threshold is greater than 1 J / cm. 2 @1550nm.

[0056] See also Figure 1 As shown, along the preset direction, the adjustment module 2 may also include a polarization-maintaining wavelength division multiplexer 22, a polarization-maintaining circulator 23, and a first coupler 24.

[0057] The polarization-maintaining wavelength division multiplexer 22 is connected to the output of the pump source 1 and is used to guide the laser into the annular cavity and maintain the polarization direction of the laser inside the annular cavity. The polarization-maintaining wavelength division multiplexer 22 can be a 980nm / 1550nm polarization-maintaining wavelength division multiplexer, with its 980nm port connected to the output of the pump source 1.

[0058] The pulse-state controllable laser system also includes a saturable absorber 4 and a polarization-maintaining fiber 5. The first port of the polarization-maintaining circulator 23 is located in the output optical path of the polarization-maintaining wavelength division multiplexer 22, the second port of the polarization-maintaining circulator 23 is connected to the saturable absorber 4 and the polarization-maintaining fiber 5 in sequence, and the third port of the polarization-maintaining circulator 23 is connected to the high-speed adjustable interference component 21.

[0059] Specifically, the polarization-maintaining circulator 23 can be a three-port polarization-maintaining circulator, which is a multi-port non-reciprocal optical device where light can only propagate in one direction. The signal light output from the polarization-maintaining wavelength division multiplexer 22 enters the first port of the polarization-maintaining circulator 23, exits from the second port, passes through the tapered saturable absorber 4 and the polarization-maintaining fiber 5, and is reflected by the polarization-maintaining fiber 5 before being output from the second port to the third port, and then again from the third port to the high-speed tunable interference component 21. The polarization-maintaining circulator 23 can operate at a wavelength of 1550±30nm, has an isolation of >40dB, and can withstand an optical power of >1W.

[0060] In one feasible implementation, the polarization-maintaining fiber 5 can be a polarization-maintaining fiber Bragg grating, and the tapered saturable absorber 4 can be fabricated using a tapered single-mode polarization-maintaining fiber, with Cr2S3 powder uniformly sprinkled onto the fiber. The signal light is input to the tapered saturable absorber 4 through the second port of the polarization-maintaining circulator 23, then reflected back to the saturable absorber 4 by the polarization-maintaining fiber Bragg grating and finally returns to the second port of the circulator 23. During this process, the pump light passes through the saturable absorber 4 twice, which is beneficial for enhancing the nonlinear effect within the ring cavity, thereby realizing multi-pulse soliton molecules.

[0061] When a polarization-maintaining fiber Bragg grating is placed in a conical saturable absorber 4, the reflectivity is >99% and the damage threshold is >0.3 J / cm. 2 @1550nm, without changing the polarization state of the ring cavity, can increase the net dispersion within the ring cavity, thereby reducing the fiber length within the ring cavity and increasing the repetition frequency of the mode-locked pulse. A higher repetition frequency is beneficial for dissipative soliton molecules to interfere more easily within the FP cavity 213, generating high peak power pulses.

[0062] The first coupler 24 is located between the high-speed tunable interferometer 21 and the polarization-maintaining wavelength division multiplexer 22. The first coupler 24 is used to transmit the laser output from the high-speed tunable interferometer 21 back to the polarization-maintaining wavelength division multiplexer 22. The first coupler 24 is also configured to output the laser.

[0063] Specifically, along a preset direction, the first coupler 24 is positioned after the high-speed adjustable interference component 21 and is used to output the laser power in the annular cavity according to a preset ratio, such as 7:3, 8:2, or 9:1, where 70%, 80%, or 90% is used to circulate in the annular cavity and 30%, 20%, or 10% is output.

[0064] See also Figure 1 As shown, in some feasible implementations, the adjustment module 2 may also include polarization-maintaining erbium-doped gain fiber 25, polarization-maintaining filter 26, polarization-maintaining isolator 27, and polarization-maintaining dispersion compensation fiber 28.

[0065] The polarization-maintaining erbium-doped gain fiber 25 and the polarization-maintaining filter 26 are sequentially arranged between the polarization-maintaining wavelength division multiplexer 22 and the polarization-maintaining circulator 23 according to a preset direction. Along the preset direction, the polarization-maintaining erbium-doped gain fiber 25 is positioned after the polarization-maintaining wavelength division multiplexer 22, exhibiting a second-order dispersion of approximately 28.04 ps at 1550 nm. 2 / km, typical erbium-doped fibers can produce gains of up to or exceeding 20dB at pump power in the 980nm band, providing sufficient gain for pulse-controlled laser systems. Among them, the polarization-maintaining erbium-doped gain fiber 25 can be the polarization-maintaining erbium-doped gain fiber PM-EDF (Er80-4 / 125-HD-PM).

[0066] Along a predetermined direction, a polarization-maintaining filter 26 is positioned after the erbium-doped polarization-maintaining gain fiber 25. The polarization-maintaining filter 26 includes a high-performance thin-film filter with a bandwidth of 10 nm. In a laser system with controllable pulse states, setting the polarization-maintaining filter 26 is beneficial for generating multi-pulse soliton molecules, ensuring stability and reliability. At the same time, the narrow-band polarization-maintaining filter 26 can be used to shield the spontaneously amplified radiation noise signal in the erbium-doped polarization-maintaining gain fiber.

[0067] Specifically, the laser generated by the pump source 1 includes a pump laser and a pulsed laser. After passing through the polarization-maintaining dispersion compensation fiber 28, the pump laser is absorbed by the polarization-maintaining dispersion compensation fiber 28, and the output laser is a pulsed laser. The remaining pump laser is absorbed by a polarization-maintaining filter 26 placed in the optical path.

[0068] The polarization maintaining isolator 27 is positioned between the polarization maintaining circulator 23 and the high-speed adjustable interference assembly 21.

[0069] Specifically, the polarization-maintaining isolator 27 is positioned after the third port of the polarization-maintaining circulator 23 to achieve unidirectional transmission of the optical signal. The polarization-maintaining isolator 27 operates at a center wavelength of 1550±20nm, employing a fast-axis cutoff and slow-axis transmission mode to maintain the polarization state stability of the input light. It can continuously withstand optical power greater than 1W and has an isolation degree greater than 40dB. This polarization-maintaining isolator 27 is used to suppress backpropagation light generated by beam interference and end-face reflection within the FP cavity 213, preventing high-peak-power pulse back propagation and avoiding damage to optical components. It also improves the stability and unidirectional operation characteristics of the pulse-state controllable laser system. This polarization-maintaining isolator 27 can be a high-peak-power polarization-maintaining isolator. To achieve tunable generation of dissipative solitons and anomalous waves, the FP cavity 213 provided in this embodiment is positioned after the polarization-maintaining isolator 27.

[0070] The polarization-maintaining dispersion-compensating fiber 28 is disposed between the first coupler 24 and the polarization-maintaining wavelength division multiplexer 22.

[0071] Specifically, along a preset direction, the polarization-maintaining dispersion-compensating fiber 28 is positioned after the first coupler 24, and its second-order dispersion at 1550 nm is approximately 70.2 ps. 2 / km is used to control the net dispersion within the ring cavity to meet the conditions for the generation of dissipative soliton molecules. At the same time, its core diameter of 2.1μm is smaller than that of polarization-maintaining single-mode fiber and polarization-maintaining erbium-doped gain fiber. This core diameter corresponds to a higher nonlinear coefficient, which is beneficial to the generation of dissipative soliton molecules and anomalous waves.

[0072] The pulse-state controllable laser system also includes a second coupler 6 and a first high-speed photodetector 7, which are located sequentially between the adjustment module 2 and the FPGA microcontroller 3.

[0073] The second coupler 6 is connected between the first coupler 24 and the first high-speed photodetector 7 in the adjustment module 2. The second coupler 6 is used for laser beam splitting. Most of the laser beam is used for output, and a small portion of the laser beam is converted into a corresponding voltage signal by the first high-speed photodetector 7 and received by the FPGA microcontroller 3. The data processing module of the FPGA microcontroller 3 can calculate the time-domain waveform of the incident light detected by the first high-speed photodetector 7 based on the received voltage signal through analog-to-digital conversion. Through calibration calculation, the peak power and pulse spacing of the laser system output pulse with controllable pulse state can be obtained. The output end of the second coupler 6 can be connected to an output window or an output mirror.

[0074] The first high-speed photodetector 7 is disposed between the second coupler 6 and the FPGA microcontroller 3. The first high-speed photodetector 7 is used to detect the output light, and the second photodetector 8 is disposed between the pump light source 1 and the FPGA microcontroller 3. The second photodetector 8 is used to pump the laser.

[0075] The 980nm pump light is split into 10% portions by a coupler and received by a second photodetector 8 with a response wavelength of 980nm. The second photodetector 8 can contain a small-volume, fast-response, high-quantum-efficiency photodiode. When laser light is incident on the photodiode, photogenerated carriers are generated. These carriers diffuse to produce a photocurrent. and incident light power P L Ratio of response for:

[0076] ;

[0077] Determined by the performance of the photodiode itself, the photocurrent is then output as a voltage signal to the FPGA microcontroller via a transimpedance amplifier. ,in The FPGA microcontroller 3 determines the value of the feedback resistor based on the received data. The incident light power detected by the second photodetector 8 is obtained through analog-to-digital conversion. Then, the output power value of the laser system with controllable pulse state is obtained through calibration calculation. Since the actual output power of the controllable pulse state laser system deviates significantly from the set power, the FPGA microcontroller 3 calculates the power output value according to the PID control algorithm and converts it into the current value driving the laser system with controllable pulse state, achieving the desired control effect. This closed-loop control of the pump power maps the final output pump power to the driving current control quantity through the PID algorithm, ensuring the stability of the pump power after the generation of dissipative soliton molecules.

[0078] It should be emphasized that, please continue to refer to Figure 1 As shown in the embodiment of this application, the connection relationship between various devices is represented by different linear representations in the pulse-state controllable laser system. Dashed lines indicate wire connections, while solid lines indicate fiber optic connections. The fiber optic cable can be a polarization-maintaining passive fiber, such as PM1550, with a second-order dispersion value of approximately -20.5 ps at 1550 nm. 2 / km, used for connections between devices, using polarization-maintaining fiber 5 configuration, to achieve essentially maintenance-free laser operation.

[0079] Figure 3 This is a schematic diagram of the control flow of the electronic control part in an FPGA microcontroller provided in an embodiment of this application.

[0080] Among some feasible implementation methods, see Figure 3 As shown, the FPGA microcontroller 3 can be used to control the pump power of the pump source 1, the cavity length of the FP cavity 213, and the gas pressure of the FP cavity 213 in a three-way cyclic adjustment, realizing multi-parameter coordinated stable control. Each electrical control quantity establishes a quantitative correspondence with the physical quantity through the mapping relationship of electrical parameters, thereby ensuring that the laser system with controllable pulse state has computability and repeatability.

[0081] In the control of the pump light source 1, the FPGA microcontroller 3 may include a pump current regulation submodule, which is based on the current signal. I pump Send current signal to pump light source 1 I p Pump light source 1 is based on current signal. I p Adjust the output power, including 10% of the optical power. P L The signal is transmitted to the second photodetector 8 and the voltage signal is transmitted to the second photodetector 8. V OUTThe output is sent to the pump current control submodule. Additionally, the first high-speed photodetector 7 is also used to receive the output laser power. P L1 The output laser of a pulse-state controllable laser system, and the voltage signal V OUT1 Output to FPGA microcontroller 3.

[0082] In the control of the moving part 215, for the FP cavity 213, the base 214 can be an electric control platform, and the moving part 215 can be connected to the output of the stepper motor to drive the FP cavity 213 to move in 0.1mm steps. The specific steps are as follows: first, the FPGA microcontroller 3 outputs a pulse signal to make the stepper motor rotate clockwise. V cw Or a pulse signal that rotates counterclockwise V ccw Each output corresponds to a pulse, causing the stepper motor to rotate 1° clockwise or counterclockwise, corresponding to a 0.1mm rightward or leftward displacement of the FP cavity 213, increasing or decreasing the length within the FP cavity 213 by 0.1mm. The operating sequence from the FPGA microcontroller 3 to the stepper motor operation module is as follows: the output processing module of the FPGA microcontroller 3 provides the stepper motor pulse drive control submodule with a single pulse signal for clockwise or counterclockwise rotation. The stepper motor pulse drive submodule then provides the stepper motor with a corresponding duration of A-phase or B-phase current, driving the stepper motor to rotate 1° clockwise or counterclockwise. Simultaneously, the stepper motor includes an encoder, which feeds back the stepper motor's operating status to the stepper motor pulse drive control submodule to confirm whether the stepper motor is operating according to the predetermined signal. In this way, after the dissipative soliton molecules are generated, the cavity length of the FP cavity 213 is controlled by a stepper motor. In particular, the design of filling the FP cavity 213 with air is added to enhance the nonlinear effect in the annular cavity, which is beneficial to the formation of an anomalous wave with a peak value after the dissipative soliton molecules interfere in the FP cavity 213.

[0083] In the control of the air source 216, the adjustment and control of the air pressure in the FP cavity 213 is achieved by the air pressure boosting output from the data drive module in the FPGA microcontroller 3. W i Or lower blood pressure W d The gas pressure regulation command is sent to the gas drive submodule, which then sends an inflation command to the miniature proportional valve inside the FP chamber 213. V i Or send a venting command to the electromagnetic pressure relief valve. V d To adjust the pressure of the regulating gas (such as argon) inside the FP cavity 213, thereby changing the refractive index inside the FP cavity 213. nThe gas pressure sensing module integrates a piezoresistive pressure sensor into a miniature proportional valve, utilizing the piezoresistive effect of monocrystalline silicon. Using integrated circuit technology, a set of equivalent resistors is diffused in a specific direction on a monocrystalline silicon diaphragm, and these resistors are connected in a bridge circuit. The monocrystalline silicon diaphragm is placed inside the sensor cavity. When the pressure changes, the monocrystalline silicon undergoes strain, causing the strain resistors diffused directly on it to change in a manner proportional to the measured pressure. The corresponding voltage output signal is then obtained by the bridge circuit. ,in The voltage difference at the output terminals of the bridge is... R 1 , R 2 , R 3 The impedances of the three bridge arms are known. R X The change in pressure sensor readings causes a change in the bridge output voltage, which is then amplified by an amplifier and converted by a resistor. R in Converted to current I in Then through a precision resistor R s The corresponding voltage signal is obtained. V l The digital quantity corresponding to the voltage signal is obtained through the analog-to-digital converter of the FPGA microcontroller 3. The FPGA microcontroller 3 processes the digital quantity according to a preset current-pressure linear mapping relationship or a calibrated conversion formula, thereby calculating the pressure value corresponding to the current sensor output current, realizing the digital acquisition and identification of the pressure signal. When the air pressure inside the FP cavity 213 is lower than the reference value... Y X At that time, FPGA microcontroller 3 sends an air pressure regulation command. W i The micro proportional valve is opened to increase the air pressure inside the chamber. When the air pressure inside the FP chamber 213 increases beyond the reference value, the FPGA microcontroller 3 will send an air pressure regulation command. W d Open the pressure relief valve to reduce the air pressure inside the chamber, so that the air pressure inside the FP chamber 213 is maintained at the reference air pressure, and the air pressure is stabilized at ±0.1 kPa of the reference size.

[0084] Corresponding to the above-described embodiment of a pulse-state controllable laser system, this application also provides an embodiment of a control method for a pulse-state controllable laser system. This control method can generate dissipative soliton molecules in a ring cavity, adjust the FP cavity to introduce spatial light to generate interference, and then regulate the output state of the pulse-state controllable laser system so that the abnormal wave and dissipative soliton molecules can be output controllably according to a predetermined frame structure, thereby realizing encrypted signal transmission.

[0085] Figure 4 This is a flowchart illustrating a control method for a pulse-state controllable laser system provided in an embodiment of this application.

[0086] See Figure 4 As shown, the control method for a pulse-state controllable laser system provided in this application embodiment may include the following steps S1 to S5.

[0087] Step S1: With the FP cavity length in its initial bonding state and the air pressure inside the FP cavity at standard air pressure, control the pump light source to adjust the pump power using the first set. In the initial bonding state, the fixed fiber and the movable fiber of the FP cavity are bonded at their opposite ends, and the FP cavity length is zero.

[0088] Specifically, the initial bonding state of the FP cavity length can be achieved by controlling the moving parts of the FPGA microcontroller to bond the fixed fiber end and the movable fiber end of the FP cavity, thereby realizing the initial bonding state of the FP cavity length.

[0089] In step S1, the first set is a set of multiple power values ​​formed with an initial power as the initial value and a step size as the step value. The first set... P 1 can be { P 11 , P 12 , P 13 , , , , , , , which contains multiple pump powers. P 11 The initial power is the initial step length, which is the difference between the power of adjacent pumps. For example, if the initial step length is... P 12 - P 11 The difference, or the first step length is P 13 - P 12 The difference.

[0090] The cavity length of the FP cavity is controlled to be in the initial mating state. The fast and slow axes of the first reflecting surface of the fixed fiber and the second reflecting surface of the movable fiber are perfectly aligned, and there is no spatial light within the entire FP cavity. The FPGA microcontroller increases the pump power of the pump light source using the first set, and the output port can generate the initial pulse spacing.

[0091] Step S2: In response to the target pulse spacing being less than the initial pulse spacing, the pump source is controlled to maintain a constant target power. Adjusting gas is introduced into the FP cavity to regulate the FP cavity pressure within a preset range, and the cavity length is adjusted using a second set of values. The initial pulse spacing is the pulse spacing corresponding to the initial power, and the second set is a set of multiple cavity lengths formed with zero as the initial value and a second step size as the step value. The initial pulse spacing is the pulse spacing corresponding to the laser output in the first pulse state, which includes the dissipative soliton molecule state of the laser. Thus, by employing an adjustable FP cavity design within the annular cavity of a laser system with controllable pulse states, and with the two fiber end faces coated and the FP cavity length zero, high signal-to-noise ratio dissipative soliton molecules can be achieved, improving the stability of signal transmission.

[0092] Specifically, step S2 may include steps S21 and S22.

[0093] Step S21: Using the time-stepping method, the pulse state of the laser is determined by combining the nonlinear Schrödinger equation with the cavity length, refractive index and target power of the FP cavity; wherein, the refractive index of the FP cavity is obtained by adjusting the gas pressure of the FP cavity.

[0094] In this step, combined Figure 1 The schematic diagram of the pulse-state controllable laser system is shown. A corresponding model is constructed using a lumped iterative mapping model, where intracavity components act sequentially according to their actual physical order. Within each fiber segment (PM1550, PM200D, and PM-EDF), pulse evolution is driven by the nonlinear Schrödinger equation of the beam propagation model.

[0095] ;

[0096] in, The amplitude of the slow change in the pulse envelope. The distance the pulse travels along the optical fiber. For Raman response time, For a time measure in a frame of reference that moves with the pulse at group velocity, The attenuation coefficient of the optical fiber. The second-order dispersion parameter of the optical fiber is given. The gain-bandwidth related time constant, This represents the gain bandwidth of the gain fiber. For the nonlinear coefficient of the optical fiber, The pulse center frequency, It is a nonlinear refractive index. c At the speed of light, This represents the effective mode field area of ​​the optical fiber. This represents the gain coefficient of the gain fiber. The small-signal gain coefficient is determined by the pump power. For pulse energy, The gain saturation energy is related to the pump power as follows: , K For efficiency parameters, For pump power, I The saturation light intensity is the gain medium.

[0097] Conical saturable absorber transfer function , E For the incident light intensity, The saturation power of a saturable absorber. The modulation depth of the saturable absorber. This represents the unsaturated loss of a saturable absorber. The intracavity transfer function of the FP is... ,in These are the first transmission amplitude coefficient and the second transmission amplitude coefficient, respectively. These are the amplitude coefficients of the first and second reflections, respectively, and α is the amplitude loss. The angular frequency of the light field. For propagation phase, L Let be the cavity length of the FP cavity. n The relationship between the change in refractive index caused by gas filling the cavity and the gas pressure inside the FP cavity is as follows: , n 0 The refractive index is at standard atmospheric pressure. Y The current air pressure. Y 0 Standard atmospheric pressure T 0 Standard temperature T The current temperature is used. This modeling method can better encapsulate the dynamic characteristics introduced by each component. Subsequently, time-stepped numerical integration methods can be used to systematically solve the model describing the propagation characteristics of optical pulses within the cavity to predict the conditions for anomalous wave generation, thereby guiding laser systems with controllable pulse states to generate anomalous waves more quickly and solving the problem of uncontrollable anomalous wave generation.

[0098] Step S22: In response to the laser outputting in a first pulse state, obtain the target pulse spacing corresponding to the first pulse state; the target pulse spacing is obtained by converting the voltage signal output by the first high-speed photodetector after receiving the laser.

[0099] In this step, as the pump power increases until dissipative soliton molecules are generated at the output pulse interval less than M1, the pulse interval at this point is recorded as the target pulse interval. At this target pulse interval, the laser outputs in the first pulse state, that is, at this point, the laser system with controllable pulse state outputs dissipative soliton molecules. Thus, the target pulse interval can be used as the critical state for the laser system with controllable pulse state to output dissipative soliton molecules.

[0100] After obtaining the target spacing, the pump light source is controlled to maintain a constant target power, and regulating gas is introduced into the FP cavity to adjust the gas pressure within a preset range. The cavity length of the FP cavity is then adjusted using a second set of parameters. The second set of parameters... L { L 1, L 2, L 3···}, L 1 represents the initial fitting state, and the second step size is the difference between the lengths of two adjacent cavities. For example, if the second step size is... L 2- L 1, or the second step length is L 3- L 2.

[0101] Figure 5 This is a comparative analysis diagram of an FP cavity before and after stretching, provided in an embodiment of this application; wherein, Figure 5 Image (a) shows a schematic diagram of the spectrum inside the FP cavity when it is not stretched. Figure 5 Figure (b) shows a schematic diagram of the spectrum after stretching inside the FP cavity.

[0102] See Figure 5 As shown in (a), after dissipative soliton molecules are generated, the FPGA microcontroller maintains the current pump power value and controls the moving component and gas source. The moving component drives the movable fiber in the FP cavity to move in 0.1mm increments, increasing the length of the FP cavity and introducing the spatial light component. During the increase in the length of the FP cavity, the fast and slow axes of the two fiber end faces in the FP cavity are aligned. Simultaneously, the gas source introduces argon gas with a concentration >95% into the FP cavity, and the FPGA microcontroller detects the gas pressure in the FP cavity to keep it within a preset range.

[0103] Step S3: Determine the target cavity length; the target cavity length is the cavity length of the FP cavity when the target peak power is greater than twice the peak power in the first pulse state; the target peak power is obtained by converting the voltage signal output by the first high-speed photodetector after receiving the laser; the target cavity length is the cavity length of the FP cavity when the laser is output in the second pulse state; the second pulse state includes the abnormal wave state of the laser.

[0104] Specifically, step S3 may include steps S31 and S32. That is, the same method can be used to determine the output state of the laser.

[0105] Step S31: Using the time-stepping method, the pulse state of the laser is determined by combining the nonlinear Schrödinger equation with the cavity length, refractive index and target power of the FP cavity.

[0106] Step S32: In response to the laser output in the second pulse state, determine the target cavity length corresponding to the second pulse state; wherein, when the laser is output in the second pulse state, the target peak power is greater than twice the peak power in the first pulse state.

[0107] In this step, see Figure 5 As shown in (b), dissipative soliton molecules first interfere within the FP cavity, generating peak power pulses that are twice or more powerful than those of the dissipative soliton molecules. Subsequently, nonlinear argon gas enhances the instability and nonlinearity of the peak power pulses, thereby generating an anomalous wave with a peak value more than twice that of the dissipative soliton molecules. After the anomalous wave is generated, the FPGA microcontroller records the cavity length of the FP cavity at this time as the target cavity length, as well as the argon gas pressure parameters within the FP cavity.

[0108] Step S4: Control the real-time pump power of the pump source to the target power and the real-time cavity length of the FP cavity to the initial fitting state, and output the laser in the first pulse state.

[0109] Step S5: Control the real-time pump power of the pump source to the target power and the real-time cavity length of the FP cavity to the target cavity length, and output the laser in the second pulse state.

[0110] In steps S4 and S5, the FPGA microcontroller can controllably switch and adjust the abnormal wave and dissipative soliton molecules. Specifically, under the pump power generated by the dissipative soliton molecules, the FP cavity is restored to the initial bonding state to realize the dissipative soliton molecules, and the FP cavity and the argon gas pressure in the cavity are adjusted to the abnormal wave generation state to realize the abnormal wave.

[0111] Furthermore, during the switching between the first pulse state and the second pulse state, the refractive index inside the FP cavity remains the same, ensuring that the change in optical path difference is only introduced by the cavity length adjustment, thus avoiding the interference of the interference phase by the refractive index disturbance.

[0112] Of course, the control method for the pulse-state controllable laser system provided in the embodiments of this application may also include step S6.

[0113] Step S6: Control the real-time pump power of the pump source to be less than the target power, and output the laser in the third pulse state; the third pulse state includes the dissipative soliton state.

[0114] Thus, by combining steps S4 to S6, the precise switching and stable output of three pulse states—dissipative soliton molecules, anomalous waves, and dissipative solitons—can be achieved through the relationship between the real-time pump power of the pump light source and the target power, the relationship between the length of the FP cavity and the target cavity, and the coordinated adjustment of the argon pressure inside the cavity.

[0115] The control method for a pulse-state controllable laser system provided in this application enables dissipative soliton molecules and anomalous waves to be output according to a predetermined frame structure. At the same time, the dissipative soliton molecules have a high signal-to-noise ratio, which is beneficial for stable demodulation at the signal receiving end. Furthermore, the controllable appearance of anomalous waves can realize secure transmission of optical communication, thereby improving the reliability and security of optical communication.

[0116] To enhance understanding of laser state switching in this application, a brief description of laser propagation within the annular cavity is provided below.

[0117] In a specific implementation, combined with Figure 1 and Figure 5 As shown in (a), the fiber end face and fast and slow axes within the FP cavity are perfectly aligned, and the cavity length is... L =0. FPGA microcontrollers are configured according to power sets. P 1{ P 11 , P 12 , P 13 ...} Increase the pump power, and at the same time, the FPGA microcontroller will record the state of the laser output pulse received by the first high-speed photodetector in real time.

[0118] The pump laser is first coupled into the ring cavity through a polarization-maintaining wavelength division multiplexer (PWM) and then passes through a 16cm erbium-doped polarization-maintaining gain fiber. The PWM fiber absorbs the 980nm pump light, outputting a signal light of approximately 1550nm. The signal light passes through a narrow-bandwidth polarization-maintaining filter to remove spontaneous amplification noise from the PWM fiber, which is beneficial for generating multi-pulse states. The signal light then enters the first port of the polarization-maintaining circulator and is output from the second port to a tapered saturable absorber for mode locking. After passing through the tapered saturable absorber, the signal light is reflected back by a polarization-maintaining fiber Bragg grating, then enters the second port of the polarization-maintaining circulator and is output from the third port. The signal light, output from the third port of the polarization-maintaining circulator, enters the polarization-maintaining isolator. The isolator operates at a wavelength of 1550 nm, effectively preventing high-peak-power pulses from propagating back to the main cavity of the pulse-controlled laser system, thus avoiding damage to optical components and improving the stability and unidirectional operation of the system. The signal light then enters the FP cavity. Initially, the FP cavity length is zero, and the fast and slow axes of the two fiber end faces are perfectly aligned. Under the control of the FPGA microcontroller, the length of the FP cavity and the pressure of the nonlinear gas within it can be increased, causing pulse interference within the cavity and generating a high-peak-power anomalous wave under strong nonlinearity. The signal light output from the FP cavity is then output through a polarization-maintaining coupler, which outputs the cavity power at ratios of 30%, 20%, or 10%. The remaining signal light passes through the polarization-maintaining dispersion-compensating fiber PM2000D. This fiber has high positive dispersion and a small core diameter, which helps to improve intracavity nonlinearity, leading to the generation of a multi-pulse state. Finally, the signal light enters the polarization-maintaining wavelength division multiplexer to achieve a loop.

[0119] Figure 6 This is a schematic diagram illustrating three pulse states of a laser provided in an embodiment of this application; wherein, Figure 6 Image (a) shows the laser output in the third pulse state. Figure 6 Image (b) shows the laser output in the first pulse state. Figure 6 Figure (c) shows the laser output in the switching state between the first pulse state and the second pulse state. The horizontal axis represents the number of intracavity cycles, and the vertical axis represents time, in picoseconds (ps).

[0120] In some feasible implementations, experimental results are predicted through numerical simulations, such as the propagation of optical solitons in a pulse-controlled laser system. Figure 6 As shown, there are three possible scenarios.

[0121] See Figure 6As shown in (a), the laser propagates as a dissipative soliton: with a gain coefficient of 1.9 and a pump power of 5.58W, the output laser is in a stable single-pulse state and the pulse repetition frequency is M1. It can be seen that the soliton evolution process is not affected by the FP cavity, which is a dissipative soliton mode-locking in a laser system with controllable pulse state.

[0122] See Figure 6 As shown in (b), the laser propagates as dissipative soliton molecules: when the gain coefficient is 2.7, corresponding to a pump power of 8.64W, the soliton splits, producing stable dissipative soliton molecules. The distance between the two pulses is 27.6ps, which is less than the pulse distance of 4.67ns at the basic repetition frequency of the pulse, and the evolution process of the soliton molecules is not affected by the FP cavity.

[0123] See Figure 6 As shown in (c), dissipative soliton molecules and anomalous waves are generated in a controllable manner: Maintaining the pump power at 8.64W, after generating dissipative soliton molecules (as shown in segment c1 of the figure), the FP cavity length is adjusted to... L x With cavity refractive index n x This generates an abnormal wave (as shown in segment c2 in the figure), and then the cavity length of the FP cavity is restored to its initial state, and the pulse inside the cavity is restored to dissipative soliton molecules (as shown in segment c3 in the figure).

[0124] The control method for a pulse-state controllable laser system provided in this application introduces a controllably generated abnormal wave morphology with high peak power as a physical layer disturbance or random segment according to a predetermined frame structure, thereby improving the reliability and security of signal transmission without affecting data segment transmission; it can output stable multi-soliton molecules with high signal-to-noise ratio and distinguishability, reducing the performance requirements of the licensed receiver, and achieving stable and reliable data demodulation at the receiver.

[0125] Figure 7 This is a flowchart illustrating a control method for a pulse-state controllable laser system, as provided in a specific implementation of this application.

[0126] See Figure 7 As shown, in a specific implementation, the control method of a pulse-state controllable laser system may include steps S701 to S706.

[0127] Step S701: Initial state: Fibers in the FP cavity are fully aligned, cavity length... L =0. FPGA microcontrollers are configured according to power sets. P 1{ P 11 , P 12 , P 13...} Increase pump power. First, obtain the mode-locked pulse. The FPGA microcontroller receives and records the output voltage and peak power of the first high-speed photodetector. P 2{ P 21 , P 22 , P 23 ... and the peak power interval M1.

[0128] In this step, the FPGA microcontroller receives and records the output voltage of the first high-speed photodetector. .

[0129] Step S702: Increase pump power to P pt This generates dissipative soliton molecules with a pulse spacing less than M1. The FPGA microcontroller records the FP cavity length, intracavity pressure, and pump power to a dataset. L , A 0 , P pt The dataset serves as the initial setting for modulation parameters, and a transmission equation is constructed to describe the propagation characteristics of optical pulses within a laser system with controllable pulse states.

[0130] In this step, the transport equation is:

[0131] .

[0132] Step S703: Establish the corresponding FP cavity length L Changes in the gas pressure inside the cavity cause changes in the refractive index. n The transfer function.

[0133] The transfer function is , .

[0134] Step S704: Using a time-stepped numerical integration method, systematically solve the extended propagation equation describing the propagation characteristics of the optical pulse within the cavity. The model is based on the dataset { L 0 , n x , P pt Dissipative soliton molecules are obtained from the dataset {}. The FP cavity length and refractive index are adjusted in the model. L x , n x , P pt The peak output power is greater than} P xMore than three times the abnormal wave.

[0135] Step S705: FP cavity length is set according to the preset displacement step size. L { L 1, L 2, L 3. The FPGA microcontroller controls the refractive index of the light transmission within the cavity to remain constant. n x The data processing module records the peak power change in real time. When the FP cavity length increases to L x When the peak power exceeds the set of peak power of the mode-locked pulse, the peak power is obtained. P x More than three times the abnormal wave.

[0136] In this step, the refractive index is n x At that time, the corresponding pressure is Y X Set the reference pressure of the FPGA microcontroller to be Y X As the FP cavity length increases, the FPGA microcontroller continuously injects argon gas into the FP cavity to maintain the refractive index of light transmission within the cavity. n x The FPGA microcontroller's data processing module records the peak power changes in real time. When the FPGA cavity length increases to L x At times, such as Figure 5 As shown in (b), the set of peak power exceeding the peak power of the mode-locked pulse is obtained. P x An abnormal wave more than three times the normal value was then controlled by a stepper motor to keep the FP cavity length between zero and... L x The rapid switching between anomalous waves and dissipative soliton molecules enables switching according to a predetermined frame structure, with a response time of <1μs, switching consistency of ±1%, and data segment signal-to-noise ratio >50dB.

[0137] Step S706: By adjusting the pump power, FP cavity length and cavity refractive index, a signal with a high signal-to-noise ratio can be obtained that can output according to a predetermined frame structure, so that the multi-pulse spacing of the signal segment output is less than M1, and the abnormal band can output a high peak power abnormal wave with more than three times the peak power of the signal.

[0138] The control method of this pulse-state controllable laser system improves the security of system signal transmission without affecting data segment transmission by introducing controllably generated anomalous wave morphologies with high peak power as physical layer disturbances or random segments according to a predetermined frame structure. This pulse-state controllable laser system can output stable multi-soliton molecules, which have high signal-to-noise ratio and distinguishability, reducing the performance requirements of the licensed receiver, while achieving stable and reliable data demodulation at the receiver.

[0139] It should be noted that, upon considering the specification and practicing the application disclosed herein, those skilled in the art will readily conceive of other embodiments of this application. This application is intended to cover any variations, uses, or adaptations of this application that follow the general principles of this application and include common knowledge or customary techniques in the art not disclosed herein.

[0140] It should be understood that this application is not limited to the precise structure described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The true scope is indicated by this application.

Claims

1. A control method for a pulse-state controllable laser system, characterized in that, include: When the cavity length of the FP cavity is in the initial fitting state and the air pressure inside the FP cavity is the standard air pressure, the pump light source is controlled to adjust the pump power with the first set. The first set is a set of multiple power values ​​formed with an initial power as the initial value and a first step size as the step value; In response to the target pulse spacing being less than the initial pulse spacing, the pump light source is controlled to maintain a constant target power. A regulating gas is introduced into the FP cavity to adjust the gas pressure within a preset range, and the cavity length of the FP cavity is adjusted using a second set. The initial pulse spacing is the pulse spacing corresponding to the initial power, and the second set is a set of multiple cavity lengths formed with the initial bonding state as the initial value and the second step size as the step value. The initial pulse spacing is the pulse spacing corresponding to when the laser is output in a first pulse state, where the first pulse state includes the dissipative soliton molecule state of the laser. The target cavity length is determined; the target cavity length is the cavity length of the FP cavity when the target peak power is greater than twice the peak power in the first pulse state; the target peak power is obtained by converting the voltage signal received by the laser and output by the first high-speed photodetector; the target cavity length is the cavity length of the FP cavity when the laser is output in the second pulse state; the second pulse state includes the abnormal wave state of the laser; The real-time pump power of the pump light source is controlled to the target power and the real-time cavity length of the FP cavity is in the initial fitting state, and the laser is output in the first pulse state; The real-time pump power of the pump light source is controlled to be the target power and the real-time cavity length of the FP cavity is controlled to be the target cavity length, and the laser is output in the second pulse state.

2. The control method for a pulse-state controllable laser system according to claim 1, characterized in that, In response to the target pulse spacing being less than the initial pulse spacing, including: The pulse state of the laser is determined by using a time-stepping method and combining the nonlinear Schrödinger equation with the cavity length, refractive index, and target power of the FP cavity; wherein the refractive index of the FP cavity is obtained by adjusting the gas pressure of the FP cavity; In response to the laser being output in the first pulse state, the target pulse spacing corresponding to the first pulse state is obtained; the target pulse spacing is obtained by converting the voltage signal output by the first high-speed photodetector after receiving the laser.

3. The control method for a pulse-state controllable laser system according to claim 2, characterized in that, Determining the target cavity length includes: The pulse state of the laser is determined by using a time-stepping method and combining the nonlinear Schrödinger equation with the cavity length, refractive index, and target power of the FP cavity. In response to the laser being output in the second pulse state, a target cavity length corresponding to the second pulse state is determined; wherein, when the laser is output in the second pulse state, the target peak power is greater than twice the peak power in the first pulse state.

4. The control method for a pulse-state controllable laser system according to claim 3, characterized in that, In the first pulse state and the second pulse state of the laser, the refractive index inside the FP cavity is the same.

5. The control method for a pulse-state controllable laser system according to claim 1, characterized in that, The control method for the pulse-state controllable laser system further includes: The real-time pump power of the pump source is controlled to be less than the target power, and the laser is output in a third pulse state; the third pulse state includes a dissipative soliton state.

6. A laser system with controllable pulse state, characterized in that, The control method of the pulse-state controllable laser system as described in any one of claims 1-5, wherein the pulse-state controllable laser system comprises: A pump source is configured to generate laser light; An adjustment module is provided, the input end of which is connected to the pump light source. The adjustment module is provided with an annular cavity, and the laser is transmitted in a preset direction within the annular cavity. The adjustment module includes a high-speed adjustable interference component; the high-speed adjustable interference component includes an FP cavity fixed fiber and an FP cavity movable fiber arranged opposite to each other, the FP cavity movable fiber being movable relative to the FP cavity fixed fiber to form an FP cavity between the FP cavity fixed fiber and the FP cavity movable fiber; An FPGA microcontroller is connected to the adjustment module. The FPGA microcontroller is configured to control the adjustment module to switch the pulse state of the laser based on the pump power of the pump source and the cavity length of the FPGA cavity. The pulse state includes a first pulse state and a second pulse state.

7. The pulse-state controllable laser system according to claim 6, characterized in that, The high-speed adjustable interference component also includes a base, a movable component, and an air source; the movable component is disposed on the base. The fixed fiber of the FP cavity is fixed to the base, and the movable fiber of the FP cavity is disposed on the moving part. The moving part is configured to drive the movable fiber of the FP cavity to move closer to or further away from the fixed fiber of the FP cavity in order to adjust the cavity length of the FP cavity. The gas source is connected to the FP cavity and is configured to introduce regulating gas into the FP cavity to regulate the gas pressure in the FP cavity.

8. The pulse-state controllable laser system according to claim 6, characterized in that, The fixed fiber in the FP cavity includes a first end face, and the movable fiber in the FP cavity includes a second end face, with the first end face and the second end face disposed opposite to each other. The first end face is coated with a first reflective film, and the second end face is coated with a second reflective film, wherein both the first reflective film and the second reflective film include a multilayer dielectric film structure.

9. The pulse-state controllable laser system according to claim 6, characterized in that, The adjustment module also includes a polarization-maintaining wavelength division multiplexer, a polarization-maintaining circulator, and a first coupler arranged sequentially along the preset direction; The polarization-maintaining wavelength division multiplexer is configured to guide the laser into the annular cavity; The pulse-state controllable laser system also includes a saturable absorber and a polarization-maintaining fiber; The first port of the polarization-maintaining circulator is located in the output optical path of the polarization-maintaining wavelength division multiplexer; the second port of the polarization-maintaining circulator is connected in sequence to the saturable absorber and the polarization-maintaining fiber; and the third port of the polarization-maintaining circulator is connected to the high-speed adjustable interference component. The first coupler is located between the high-speed tunable interferometer and the polarization-maintaining wavelength division multiplexer. The first coupler is configured to transmit the laser output from the high-speed tunable interferometer back to the polarization-maintaining wavelength division multiplexer. The first coupler is also configured to output the laser.

10. The pulse-state controllable laser system according to claim 9, characterized in that, The adjustment module also includes polarization-maintaining erbium-doped gain fiber, polarization-maintaining filter, polarization-maintaining isolator, and polarization-maintaining dispersion compensation fiber; The polarization-maintaining erbium-doped gain fiber and the polarization-maintaining filter are sequentially arranged between the polarization-maintaining wavelength division multiplexer and the polarization-maintaining circulator in a preset direction. The polarization-maintaining isolator is disposed between the polarization-maintaining circulator and the high-speed adjustable interference component; The polarization-maintaining dispersion compensation fiber is disposed between the first coupler and the polarization-maintaining wavelength division multiplexer. The pulse-state controllable laser system further includes a second coupler and a first high-speed photodetector, which are sequentially disposed between the adjustment module and the FPGA microcontroller.

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