Device and method of 2-micron multimode fiber laser seed source for space communication

Abstract

The invention provides a device and method of a 2-micron multimode fiber laser seed source for space communication. The device comprises a PC control subsystem, a laser generation subsystem, a pumping control subsystem, a polarization control subsystem and a time domain-frequency domain-space domain feedback subsystem. The PC control subsystem controls each device to work; the laser generation subsystem is used for generating laser pulses; the pumping control subsystem controls the pumping output power; the polarization control subsystem is used for adjusting an intracavity polarization state and is matched with the laser generation subsystem to regulate and control required laser pulses; and the time domain-frequency domain-space domain feedback subsystem is used for remotely controlling an oscilloscope, a spectrograph and a CCD (Charge Coupled Device) camera, acquiring image data and feeding information back to the PC control subsystem. The method has the advantages of being low in building cost, good in compatibility, high in precision and the like, and meanwhile adaptability, reliability and self-adjustment of the laser seed source in a complex space environment can be achieved through an intelligent control system based on the combination of the genetic algorithm and the neural network.

Description

Technical Field

[0001] The present invention relates to the fields of optical fiber laser control technology and space communication technology, and in particular to a device and method for a 2-micron multimode optical fiber laser seed source for space communication. Background Art

[0002] With the rapid development of aerospace technology and space exploration, the demand for high-speed, large-capacity, and highly confidential data transmission in space communications is growing exponentially. As a core component of space optical communication systems, the performance of fiber laser sources directly impacts the quality and reliability of communication links. Lasers in the 2-micron band, with their significant advantages such as low atmospheric transmission loss, ultra-long gain bandwidth (300+nm), long-distance transmission, anti-interference capabilities, and eye safety, have shown great application potential in the field of space communications and have become a hot research topic.

[0003] However, existing 2-micron fiber laser seed source generation technology faces numerous challenges. On the hardware level, traditional laser seed source devices often rely on specially customized optical fibers, which are costly and time-consuming to produce, making them difficult to meet the rapidly developing needs of space communications. Furthermore, the generation of multimode fiber laser seed sources presents challenges such as mode instability, limited output power, and poor beam quality, severely hindering the performance improvement of space communication systems. Furthermore, the complexity of the space environment, such as strong radiation and extreme temperature fluctuations, places stringent demands on the stability and reliability of laser seed sources.

[0004] With the widespread application of AI technology and closed-loop feedback control in the aerospace field, the limitations of existing laser source control systems have become increasingly prominent. On the one hand, the data acquisition and processing links lack automated integration, and the manually intervened data storage and analysis processes are inefficient, making it impossible to achieve real-time data feedback and intelligent decision-making. On the other hand, the traditional open-loop control mode cannot dynamically adapt to changes in the space environment, and it is difficult to quickly correct the output parameters of the laser source through the closed-loop feedback mechanism, which greatly affects the reliability and continuity of the space communication link. Therefore, the development of a 2-micron multimode fiber laser seed source generation device and method that can utilize commercial multi-type optical fibers and integrate AI intelligent algorithms with high-precision closed-loop feedback control has become the key to breaking through the current technical bottleneck and promoting the upgrading of space communication technology. Summary of the Invention

[0005] In response to the above-mentioned technical deficiencies, the purpose of the present invention is to provide a device and method for a 2-micron multimode fiber laser seed source for space communication, to provide a highly stable and efficient laser seed source for space communication systems, and to promote the development and application of space optical communication technology in the fields of data transmission, remote sensing detection, etc.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] A device for a 2-micron multimode fiber laser seed source for space communications, comprising:

[0008] The PC control subsystem uses genetic algorithms and neural networks as decision-making centers to build a master control terminal on the Python platform for two-way data communication with external devices and control the operation of external devices;

[0009] The laser generation subsystem is configured with a closed-loop optical path and is connected to the pump control subsystem to generate the laser pulses required for space communication;

[0010] The pump control subsystem is connected to the PC control subsystem and is used to receive control and feedback signals from the PC control subsystem and control the pump output power;

[0011] The polarization control subsystem is connected to the PC control subsystem and the laser generation subsystem, and is used to receive and execute feedback and control signals from the PC control subsystem, adjust the polarization state in the cavity, and cooperate with the laser generation subsystem to control the required laser pulses;

[0012] The time-frequency-space domain feedback subsystem is connected to the PC control subsystem and the polarization control subsystem, receives feedback and control signals from the PC control subsystem, collects time-domain, frequency-domain, and space-domain information of the laser pulse, and feeds it back to the PC control subsystem.

[0013] Preferably, the PC control subsystem includes a laptop computer installed with a Python software platform; the laptop computer communicates with external devices through an RS-232 interface, a USB interface, a Bluetooth interface, a network interface LAN or a GPIB interface; and the Python software platform integrates a decision-making center based on genetic algorithms and neural networks.

[0014] Preferably, the laser generating subsystem comprises:

[0015] The pump combiner, gain fiber, single-mode fiber, multimode output coupler, few-mode fiber, polarizer and optical isolator are fused in sequence;

[0016] The gain fiber is a thulium-doped fiber or a thulium-holmium co-doped fiber, and the emission wavelength range is 1850-2500nm;

[0017] The single-mode fiber is a standard undoped single-mode fiber;

[0018] The core of the multimode output coupler is 50 μm, and has a high output end feedback loop and a low output end monitoring channel; the multimode output coupler has one input end and two output ends;

[0019] The core of the few-mode fiber is 14, 18 or 20 μm, which is used to produce saturable absorption effect in the cavity with the multimode output coupler;

[0020] The polarizer is used to generate polarization effect in the cavity, and the light output from the low output end will enter the photodetector to detect the time domain signal;

[0021] The laser output by the laser generation subsystem contains different spatial modes, including LG 01 , LG 11 beam, while temporally locked to the pulse train.

[0022] Preferably, the pump control subsystem includes:

[0023] A pump source with a central wavelength of 793nm; the input end of the pump combiner is connected to the laser output end of the pump source by fusion splicing; the pump combiner couples the output light of the pump source and the output light after passing through the optical isolator into an optical fiber, which is connected to the gain fiber; the pump source is a remotely controlled semiconductor laser, whose central wavelength can be drift-controlled by adjusting the temperature, and has an external port, specifically RS-232 or USB3.0, which can develop communication protocols including 793nm wavelength and output power up to 12W;

[0024] The first external auxiliary communication device is installed on the pump source, connected to the PC control subsystem, and supports RS-232 or USB3.0 communication protocol.

[0025] Preferably, the polarization control subsystem includes:

[0026] a first electronic polarization controller, a second electronic polarization controller, and a third electronic polarization controller; the first and second electronic polarization controllers are wound around a 1-3 m single-mode optical fiber in a paddle form or an extrusion form, with the number of blades being greater than or equal to two, and are manually rotated and adjusted to drive the blades to rotate or squeeze to produce a phase change within a range of 0-2π; the third electronic polarization controller is wound around a 1-3 m few-mode optical fiber in a paddle form or an extrusion form, with the number of blades being greater than or equal to two, and are input with a voltage signal to drive the blades to rotate or squeeze to produce a phase change within a range of 0-2π, and the drive circuit thereof has an external communication function compatible with a Python platform or is capable of secondary development of a communication protocol through a Python platform;

[0027] A second external auxiliary communication device, a third external auxiliary communication device, and a fourth external auxiliary communication device; the second external auxiliary communication device is installed on the first electronic polarization controller; the third external auxiliary communication device is installed on the second electronic polarization controller; the fourth external auxiliary communication device is installed on the third electronic polarization controller; the second external auxiliary communication device, the third external auxiliary communication device, and the fourth external auxiliary communication device are respectively connected to the PC control subsystem.

[0028] Preferably, the time-frequency-space domain feedback subsystem includes:

[0029] Spectral analysis unit: including a spectrum analyzer and a fifth external auxiliary communication device, with a detection band of 1200-2400nm;

[0030] Time domain analysis unit: includes an oscilloscope, a sixth external auxiliary communication device and a photodetector, the input end of the photodetector is connected to the optical isolator through an optical fiber; the photodetector response band is 1.8-2.1μm; the oscilloscope is connected to the PC control subsystem through the sixth external auxiliary communication device to receive feedback and control signals from the PC control subsystem; the oscilloscope is a remote-controlled oscilloscope with an external port, which is an RS-232 or LAN cable interface or GPIB high-speed data interface. The communication interface of the oscilloscope is compatible with the communication protocol in Python, and is also compatible with external communication devices and P-based The communication protocol is developed on the Python platform; the bandwidth range of the photodetector is 100MHz to 1GHz, and the wavelength range is 1.8μm to 2.1μm; the spectrum analyzer is a remotely controlled spectrum analyzer with an external port, which can be an RS-232, LAN, or GPIB high-speed data interface. Its communication interface is compatible with the communication protocol in Python, external communication devices, and communication protocols developed based on Python. The detection wavelength range includes the 1200nm to 2400nm band; the spectrum analyzer has a power measurement mode and a power spectral density measurement mode.

[0031] Spatial domain analysis unit: includes a CCD camera, which is used to receive part of the optical signal output by the laser generation subsystem and detect the light spot situation; the laser signal is received by the optical signal input end of the spectrum analyzer, oscilloscope, and CCD camera respectively; the high output end of the multimode output coupler returns to the cavity for resonance, and the light output from the low output end will enter the CCD camera and spectrum analyzer to detect the light spot situation and spectral state respectively; the time domain, frequency domain, and spatial domain information of the laser pulse collected by the oscilloscope, spectrum analyzer, and CCD camera are fed back to the PC control subsystem, and the PC control subsystem controls the blade angle of the third electronic polarization controller and the output power of the pump source.

[0032] A method for generating a 2-micron multimode fiber laser seed source for space communications, comprising:

[0033] (1) Setting target parameters including pulse width, spectral characteristics, central wavelength, and spatial pattern through the PC control subsystem;

[0034] (2) Start the pump source in the pump control subsystem and adjust it to a preset power value;

[0035] (3) sending a control instruction to the polarization control subsystem through the PC control subsystem to adjust the polarization states of the first electronic polarization controller, the second electronic polarization controller, and the third electronic polarization controller;

[0036] (4) Synchronous acquisition through the time-frequency-space domain feedback subsystem:

[0037] Frequency domain spectrum data from spectrum analyzer, time domain pulse sequence data from oscilloscope, spatial spot distribution data from CCD camera;

[0038] (5) The collected data is fed back to the PC control subsystem, and the control parameters are generated through the neural network. The following closed-loop adjustments are made based on the genetic algorithm: the output power of the pump source, the polarization adjustment amount of the first electronic polarization controller, the second electronic polarization controller, and the third electronic polarization controller, until the time domain pulse sequence locking and spatial mode locking are achieved.

[0039] Preferably, in step (5):

[0040] The neural network is a multi-layer perceptron architecture, and the input layer includes time domain pulse width, spectral center wavelength, and mode purity characteristic parameters;

[0041] The fitness function of the genetic algorithm comprehensively evaluates the temporal stability, spectral matching and spatial pattern similarity indicators.

[0042] Compared with the prior art, the present invention has the following beneficial effects:

[0043] 1. Based on this application, a 2-micron multimode fiber laser seed source generation device is constructed using commercial multi-type optical fibers. This eliminates the need for custom-made optical fibers, significantly reduces device costs, and shortens production cycles. By precisely controlling the fiber combination and related parameters, the output power and mode of the laser seed source can be adjusted with high precision, while also achieving precise control of the laser's spatial mode, meeting the needs of diverse space communication scenarios and enhancing the applicability of lasers in the field of space communications.

[0044] 2. This application achieves multi-dimensional, real-time monitoring of a 2-micron multimode fiber laser seed source. It can acquire, in real time, information such as the laser's spatial mode distribution, spectral characteristics, and pulse timing characteristics, and rapidly analyze and process them. Feedback control is performed based on the analysis results, allowing timely adjustments to the laser seed source's operating status to ensure stable operation. Furthermore, efficient storage of monitoring data facilitates long-term operational status analysis and fault prediction, enhancing system reliability and maintainability.

[0045] 3. Based on this application, various commercial optical fibers and related optical instruments are integrated and controlled. After optimizing the system architecture and communication protocols, the device has good compatibility and facilitates the integration of new optical components and intelligent control algorithms. For example, the successful integration of an AI-based adaptive control algorithm enables the laser seed source to automatically adjust parameters according to changes in the space environment, enhancing its adaptability to complex environments, improving the system's intelligence and flexibility, and effectively promoting the development of space communication technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 It is a structural schematic diagram of the present invention;

[0047] Figure 2 The spectrum of the spatiotemporal noise-like mode locking output by the 2-micron multimode fiber laser seed source of the present invention;

[0048] Figure 3 The time-domain pulse sequence of spatiotemporal noise-like mode locking outputted by the 2-micron multimode fiber laser seed source of the present invention;

[0049] Figure 4 The radio spectrum of the spatiotemporal noise-like mode locking output by the 2-micron multimode fiber laser seed source of the present invention;

[0050] Figure 5 The beam profile of the spatiotemporal soliton mode-locked output of the 2-micron multimode fiber laser seed source of the present invention;

[0051] Figure 6 The spectrum of the spatiotemporal soliton mode locking output by the 2-micron multimode fiber laser seed source of the present invention;

[0052] Figure 7 The time-domain pulse sequence of spatiotemporal soliton mode locking outputted by the 2-micron multimode fiber laser seed source of the present invention;

[0053] Figure 8 The spectrum of the spatiotemporal soliton mode locking output by the 2-micron multimode fiber laser seed source of the present invention;

[0054] Figure 9 The beam profile of the spatiotemporal soliton mode-locked output of the 2-micron multimode fiber laser seed source of the present invention;

[0055] Figure 10Simulate the evolution of different modes of transmission in optical fiber for the 2-micron multimode fiber laser seed source of the present invention;

[0056] Figure 11 This is the beam profile simulated and output by the 2-micron multimode fiber laser seed source of the present invention.

[0057] in:

[0058] 1-1. Laptop computer; 2-1. Pump combiner; 2-2. Gain fiber; 2-3. Single-mode fiber; 2-4. Multimode output coupler; 2-5. Few-mode fiber; 2-6. Polarizer; 2-7. Optical isolator; 3-1. Pump source; 3-2. First external auxiliary communication device; 4-1-1. First electronic polarization controller; 4-1-2. Second electronic polarization controller; 4-2. Third electronic polarization controller; 4-3-1. Second external auxiliary communication device; 4-3-2. Third external auxiliary communication device; 4-3-3. Fourth external auxiliary communication device; 5-1. Spectrum analyzer; 5-2. Fifth external auxiliary communication device; 6-1. Oscilloscope; 6-2. Sixth external auxiliary communication device; 6-3. Photodetector; 7-1. CCD camera. DETAILED DESCRIPTION

[0059] The present invention will be further described below with reference to the accompanying drawings.

[0060] Example 1

[0061] like Figures 1 to 11 As shown, a device for a 2-micron multimode fiber laser seed source for space communication includes:

[0062] The PC control subsystem uses genetic algorithms and neural networks as decision-making centers to build a master control terminal on the Python platform for two-way data communication with external devices and control the operation of external devices;

[0063] The laser generation subsystem is configured with a closed-loop optical path and is connected to the pump control subsystem to generate the laser pulses required for space communication;

[0064] The pump control subsystem is connected to the PC control subsystem and is used to receive control and feedback signals from the PC control subsystem and control the pump output power;

[0065] The polarization control subsystem is connected to the PC control subsystem and the laser generation subsystem, and is used to receive and execute feedback and control signals from the PC control subsystem, adjust the polarization state in the cavity, and cooperate with the laser generation subsystem to control the required laser pulses;

[0066] The time-frequency-space feedback subsystem is connected to the PC control and polarization control subsystems. It receives feedback and control signals from the PC control subsystem, collects time-domain, frequency-domain, and space-domain information about the laser pulse, and feeds it back to the PC control subsystem. Through precise control of the algorithm within the PC control subsystem, it outputs stable space-time solitons, enabling stable output of a 2-micron laser seed source.

[0067] In this embodiment, the PC control subsystem includes a laptop computer 1-1 installed with a Python software platform; the laptop computer 1-1 communicates with external devices through an RS-232 interface, a USB interface, a Bluetooth interface, a network interface LAN or a GPIB interface; the Python software platform integrates a decision center based on genetic algorithms and neural networks.

[0068] In this embodiment, the laser generating subsystem includes:

[0069] The pump combiner 2-1, gain fiber 2-2, single-mode fiber 2-3, multi-mode output coupler 2-4, few-mode fiber 2-5, polarizer 2-6 and optical isolator 2-7 are fused in sequence;

[0070] The gain fiber 2-2 is a thulium-doped fiber or a thulium-holmium co-doped fiber, and the emission wavelength range is 1850-2500 nm;

[0071] The single-mode optical fiber 2-3 is a standard non-doped single-mode optical fiber 2-3;

[0072] The fiber core of the multimode output coupler 2-4 is 50 μm, and has a high output end feedback loop and a low output end monitoring channel; the multimode output coupler 2-4 has one input end and two output ends;

[0073] The core of the few-mode optical fiber 2-5 is 14, 18 or 20 μm and is used to cooperate with the multimode output coupler 2-4 in the cavity to produce a saturable absorption effect;

[0074] The polarizer 2-6 is used to generate a polarization effect in the cavity, and the light output from the low output end will enter the photodetector 6-3 for detecting the time domain signal;

[0075] The laser output by the laser generation subsystem contains different spatial modes, including LG01 and LG11 beams, and the pulse sequence is locked in time.

[0076] In this embodiment, the pump control subsystem includes:

[0077] A pump source 3-1 has a central wavelength of 793 nm. The input end of the pump combiner 2-1 is connected to the laser output end of the pump source 3-1 by fusion splicing. The pump combiner 2-1 couples the output light of the pump source 3-1 and the output light after passing through the optical isolator 2-7 into an optical fiber, which is connected to the gain fiber 2-2. The pump source 3-1 is a remotely controlled semiconductor laser whose central wavelength can be drift-controlled by adjusting the temperature. It has an external port, specifically RS-232 or USB 3.0, which allows the development of communication protocols that include a 793 nm wavelength and an output power of up to 12 W.

[0078] The first external auxiliary communication device 3 - 2 is installed on the pump source 3 - 1 , connected to the PC control subsystem, and supports RS-232 or USB 3.0 communication protocols.

[0079] In this embodiment, the polarization control subsystem includes:

[0080] The first electronic polarization controller 4-1-1, the second electronic polarization controller 4-1-2, and the third electronic polarization controller 4-2; the first electronic polarization controller 4-1-1 and the second electronic polarization controller 4-1-2 are wound around the 1-3m single-mode optical fiber 2-3 in the form of blades or extrusion, and the number of blades is greater than or equal to two. The blades are driven to rotate or squeeze to produce a phase change within a range through manual rotation adjustment; the third electronic polarization controller 4-2 is wound around the 1-3m few-mode optical fiber 2-5 in the form of blades or extrusion, and the number of blades is greater than or equal to two. The blades are driven to rotate or squeeze to produce a phase change within a range of 0-2π through an input voltage signal. The driving circuit thereof has an external communication function that is compatible with the Python platform or can perform secondary development of the communication protocol through the Python platform;

[0081] The second external auxiliary communication device 4-3-1, the third external auxiliary communication device 4-3-2, and the fourth external auxiliary communication device 4-3-3; the second external auxiliary communication device 4-3-1 is installed on the first electronic polarization controller 4-1-1; the third external auxiliary communication device 4-3-2 is installed on the second electronic polarization controller 4-1-2; the fourth external auxiliary communication device 4-3-3 is installed on the third electronic polarization controller 4-2; the second external auxiliary communication device 4-3-1, the third external auxiliary communication device 4-3-2, and the fourth external auxiliary communication device 4-3-3 are respectively connected to the PC control subsystem.

[0082] In this embodiment, the time-frequency-space domain feedback subsystem includes:

[0083] Spectrum analysis unit: includes a spectrum analyzer 5-1 and a fifth external auxiliary communication device 5-2, with a detection band of 1200-2400nm;

[0084] Time domain analysis unit: includes an oscilloscope 6-1, a sixth external auxiliary communication device 6-2 and a photodetector 6-3, the input end of the photodetector 6-3 is connected to the optical isolator 2-7 through an optical fiber; the response band of the photodetector 6-3 is 1.8-2.1μm; the oscilloscope 6-1 is connected to the PC control subsystem through the sixth external auxiliary communication device 6-2, and receives feedback and control signals from the PC control subsystem; the oscilloscope 6-1 is a remote-controlled oscilloscope 6-1 with an external port, which is an RS-232 or network cable interface LAN or GPIB high-speed data interface. The communication interface of the oscilloscope 6-1 is compatible with the communication protocol in Python and is also compatible with external The communication device is compatible with a communication protocol developed based on the Python platform; the bandwidth range of the photodetector 6-3 includes 100 MHz to 1 GHz, and the wavelength range includes 1.8 μm to 2.1 μm; the spectrum analyzer 5-1 is a spectrum analyzer 5-1 that can be remotely controlled and has an external port, which is an RS-232 or LAN cable interface or a GPIB high-speed data interface. Its communication interface is compatible with the communication protocol in Python, is also compatible with external communication devices, and is also compatible with the communication protocol developed based on Python. The detection wavelength range includes the 1200 nm to 2400 nm band; the spectrum analyzer 5-1 has a power measurement mode and a power spectral density measurement mode;

[0085] Spatial domain analysis unit: includes a CCD camera 7-1, which is used to receive part of the optical signal output by the laser generation subsystem and detect the light spot situation; the laser signal is received by the optical signal input end of the spectrum analyzer 5-1, the oscilloscope 6-1, and the CCD camera 7-1 respectively; the high output end of the multimode output coupler 2-4 returns to the cavity for resonance, and the light output from the low output end will enter the CCD camera 7-1 and the spectrum analyzer 5-1 to detect the light spot situation and the spectral state respectively; the time domain, frequency domain, and spatial domain information of the laser pulse collected by the oscilloscope 6-1, the spectrum analyzer 5-1, and the CCD camera 7-1 are fed back to the PC control subsystem, and the PC control subsystem regulates the blade angle of the third electronic polarization controller 4-2 and the output power of the pump source 3-1.

[0086] A method for generating a 2-micron multimode fiber laser seed source for space communications, comprising:

[0087] (1) Setting target parameters including pulse width, spectral characteristics, central wavelength, and spatial pattern through the PC control subsystem;

[0088] (2) Start the pump source 3-1 in the pump control subsystem and adjust it to a preset power value;

[0089] (3) Sending control instructions to the polarization control subsystem through the PC control subsystem to adjust the polarization states of the first electronic polarization controller 4-1-1, the second electronic polarization controller 4-1-2, and the third electronic polarization controller 4-2;

[0090] (4) Synchronous acquisition through the time-frequency-space domain feedback subsystem:

[0091] Frequency domain spectrum data from the spectrum analyzer 5-1, time domain pulse sequence data from the oscilloscope 6-1, and spatial spot distribution data from the CCD camera 7-1;

[0092] (5) The collected data is fed back to the PC control subsystem, and the control parameters are generated through the neural network. Based on the genetic algorithm, closed-loop adjustment is performed: the output power of the pump source 3-1, the polarization adjustment amount of the first electronic polarization controller 4-1-1, the second electronic polarization controller 4-1-2, and the third electronic polarization controller 4-2, until the time domain pulse sequence locking and spatial mode locking are achieved.

[0093] In this embodiment, in step (5):

[0094] The neural network is a multi-layer perceptron architecture, and the input layer contains time-domain pulse width, spectral center wavelength, and mode purity characteristic parameters;

[0095] The fitness function of the genetic algorithm comprehensively evaluates the temporal stability, spectral matching and spatial pattern similarity indicators.

[0096] Principle of the invention:

[0097] Spatiotemporal mode locking (STML) is a key mechanism for generating ultrashort pulses in multimode fiber (MMF) lasers, with potential applications in many fields. The following describes its principles from the perspectives of theoretical modeling, mode-locking conditions and operating mechanisms, and STML under large intermodal dispersion.

[0098] Distributed model: STML dynamics can be used with the (3+1)-dimensional complex cubic-quintic Ginzburg-Landau equation ((3+1)D CGLE ), the equation of motion of its normalized field envelope ψ(x,y,z,t) is:

[0099]

[0100] The left side of the equation is the conservative term, and the right side is the dissipative term. Where x, y are the transverse coordinates, z is the propagation direction, and t is the fast time; D represents dispersion, (x 2 +y 2 )ψ represents the refractive index of the graded-index (GRIN) multimode fiber, v and γ are the nonlinear coefficients, and δ, ε, β, and μ are the linear loss, nonlinear gain, spectral filtering, and nonlinear gain saturation coefficients, respectively.

[0101] Lumped model: To study the propagation of STDS within a round trip, a lumped model can be used. This model decomposes the STDS into a series of spatial modes, describing their propagation in the cavity via the generalized multimode nonlinear Schrödinger equation (GMMNLSE). Ignoring self-steepening, Raman scattering, and higher-order dispersion, and considering gain / loss, the equation is:

[0102]

[0103] Among them A p (z,t) is the electric field envelope of mode-p, is the r-order Taylor expansion of the mode-p propagation constant, g(z) is the saturation gain, n2 is the nonlinear refractive index, The inverse of the effective mode area taking into account mode overlap.

[0104] Example 2: Spatiotemporal Noise-Like Mode Locking

[0105] Through the algorithm calculation in the main control terminal, the pump source and the electronic polarization controller are controlled to accurately adjust the polarization state in the cavity and the pump output power, achieving stable spatiotemporal noise-like mode locking. Figure 2-Figure 5 .

[0106] Example 3: Space-time soliton mode locking

[0107] Through the algorithm operation in the main control terminal, the pump source and the electronic polarization controller are controlled to precisely regulate the polarization state in the cavity and the pump output power, thus achieving stable spatiotemporal soliton mode locking. Figure 6-Figure 9 .

Claims

1. A device for a 2-micron multimode fiber laser seed source for space communication, characterized in that: include: The PC control subsystem uses genetic algorithms and neural networks as decision-making centers to build a master control terminal on the Python platform for two-way data communication with external devices and control the operation of external devices; The laser generation subsystem is configured with a closed-loop optical path and is connected to the pump control subsystem to generate the laser pulses required for space communication; The pump control subsystem is connected to the PC control subsystem and is used to receive control and feedback signals from the PC control subsystem and control the pump output power; The polarization control subsystem is connected to the PC control subsystem and the laser generation subsystem, and is used to receive and execute feedback and control signals from the PC control subsystem, adjust the polarization state in the cavity, and cooperate with the laser generation subsystem to control the required laser pulses; The time-frequency-space domain feedback subsystem is connected to the PC control subsystem and the polarization control subsystem, receives feedback and control signals from the PC control subsystem, collects time-domain, frequency-domain, and space-domain information of the laser pulse, and feeds it back to the PC control subsystem.

2. The device of a 2-micron multimode fiber laser seed source for space communication according to claim 1, characterized in that: The PC control subsystem includes a laptop computer (1-1) installed with a Python software platform; the laptop computer (1-1) communicates with external devices via an RS-232 interface, a USB interface, a Bluetooth interface, a network interface LAN or a GPIB interface; and a decision center based on a genetic algorithm and a neural network is integrated in the Python software platform.

3. The device of a 2-micron multimode fiber laser seed source for space communication according to claim 1, characterized in that: The laser generating subsystem comprises: A pump combiner (2-1), a gain fiber (2-2), a single-mode fiber (2-3), a multi-mode output coupler (2-4), a few-mode fiber (2-5), a polarizer (2-6) and an optical isolator (2-7) are fused in sequence; The gain fiber (2-2) is a thulium-doped fiber or a thulium-holmium co-doped fiber, and the emission wavelength range is 1850-2500nm; The single-mode optical fiber (2-3) is a standard non-doped single-mode optical fiber (2-3); The multimode output coupler (2-4) has a fiber core of 50 μm and is provided with a high-output-end feedback loop and a low-output-end monitoring channel; the multimode output coupler (2-4) has one input end and two output ends; The few-mode optical fiber (2-5) uses a core of 14, 18 or 20 μm and is used to produce a saturable absorption effect in the cavity in conjunction with the multimode output coupler (2-4); The polarizer (2-6) is used to generate a polarization effect in the cavity, and the light output from the low output end will enter the photodetector (6-3) for detecting the time domain signal; The laser output by the laser generation subsystem contains different spatial modes, including LG01 and LG11 beams, and the pulse sequence is locked in time.

4. The device of a 2-micron multimode fiber laser seed source for space communication according to claim 3, characterized in that: The pump control subsystem includes: A pump source (3-1) having a central wavelength of 793 nm; an input end of a pump combiner (2-1) is connected to a laser output end of the pump source (3-1) by fusion splicing; the pump combiner (2-1) couples the output light of the pump source (3-1) and the output light after passing through an optical isolator (2-7) to an optical fiber, which is connected to a gain fiber (2-2); the pump source (3-1) is a semiconductor laser capable of remote control, wherein the central wavelength thereof can be drift-controlled by adjusting the temperature, and an external port, specifically RS-232 or USB3.0, is provided, and a communication protocol can be developed, including a 793 nm wavelength and an output power including 12 W; The first external auxiliary communication device (3-2) is installed on the pump source (3-1), connected to the PC control subsystem, and supports RS-232 or USB3.0 communication protocol.

5. The device of a 2-micron multimode fiber laser seed source for space communication according to claim 3, characterized in that: The polarization control subsystem includes: A first electronic polarization controller (4-1-1), a second electronic polarization controller (4-1-2), and a third electronic polarization controller (4-2); the first electronic polarization controller (4-1-1) and the second electronic polarization controller (4-1-2) are wound around a 1-3 m single-mode optical fiber (2-3) in a paddle form or an extrusion form, the number of the paddles being greater than or equal to two, and the paddles being driven to rotate or squeeze to produce a phase change within a range through manual rotation adjustment; the third electronic polarization controller (4-2) is wound around a 1-3 m few-mode optical fiber (2-5) in a paddle form or an extrusion form, the number of the paddles being greater than or equal to two, and the paddles being driven to rotate or squeeze to produce a phase change within a range of 0-2π through an input voltage signal, and the drive circuit thereof has an external communication function compatible with a Python platform or capable of secondary development of a communication protocol through a Python platform; A second external auxiliary communication device (4-3-1), a third external auxiliary communication device (4-3-2), and a fourth external auxiliary communication device (4-3-3); the second external auxiliary communication device (4-3-1) is installed on the first electronic polarization controller (4-1-1); the third external auxiliary communication device (4-3-2) is installed on the second electronic polarization controller (4-1-2); the fourth external auxiliary communication device (4-3-3) is installed on the third electronic polarization controller (4-2); the second external auxiliary communication device (4-3-1), the third external auxiliary communication device (4-3-2), and the fourth external auxiliary communication device (4-3-3) are respectively connected to the PC control subsystem.

6. The device of a 2-micron multimode fiber laser seed source for space communication according to claim 3, characterized in that: The time-frequency-space domain feedback subsystem includes: Spectrum analysis unit: including a spectrum analyzer (5-1) and a fifth external auxiliary communication device (5-2), with a detection band of 1200-2400nm; The time domain analysis unit comprises an oscilloscope (6-1), a sixth external auxiliary communication device (6-2) and a photodetector (6-3), wherein the input end of the photodetector (6-3) is connected to the optical isolator (2-7) via an optical fiber; the response band of the photodetector (6-3) is 1.8-2.1 μm; the oscilloscope (6-1) is connected to the PC control subsystem via the sixth external auxiliary communication device (6-2) to receive feedback and control signals from the PC control subsystem; the oscilloscope (6-1) is a remotely controlled oscilloscope (6-1) having an external port, which is an RS-232 or a LAN or GPIB high-speed data interface; the communication interface of the oscilloscope (6-1) can be connected to the communication protocol in Python. The optical spectrum analyzer (5-1) is a spectrum analyzer (5-1) that can be remotely controlled and has an external port, which is an RS-232 or LAN or GPIB high-speed data interface. The communication interface is compatible with the communication protocol in Python and is also compatible with external communication devices and the communication protocol developed based on Python. The detection wavelength range includes the 1200nm to 2400nm band. The optical spectrum analyzer (5-1) has a power measurement mode and a power spectral density measurement mode. The spatial domain analysis unit includes a CCD camera (7-1) for receiving part of the optical signal output by the laser generation subsystem and detecting the light spot condition; the laser signal is received by the optical signal input end of the spectrum analyzer (5-1), the oscilloscope (6-1), and the CCD camera (7-1) respectively; the high output end of the multimode output coupler (2-4) returns to the cavity for resonance, and the light output from the low output end enters the CCD camera (7-1) and the spectrum analyzer (5-1) to detect the light spot condition and the spectral state respectively; the time domain, frequency domain, and spatial domain information of the laser pulse collected by the oscilloscope (6-1), the spectrum analyzer (5-1), and the CCD camera (7-1) are fed back to the PC control subsystem, and the PC control subsystem regulates the blade angle of the third electronic polarization controller (4-2) and the output power of the pump source (3-1).

7. A method for generating a 2-micron multimode fiber laser seed source for space communication, characterized in that: include: (1) Setting target parameters including pulse width, spectral characteristics, central wavelength, and spatial pattern through the PC control subsystem; (2) starting the pump source (3-1) in the pump control subsystem and adjusting it to a preset power value; (3) Sending control instructions to the polarization control subsystem through the PC control subsystem to adjust the polarization states of the first electronic polarization controller (4-1-1), the second electronic polarization controller (4-1-2), and the third electronic polarization controller (4-2); (4) Synchronous acquisition through the time-frequency-space domain feedback subsystem: Frequency domain spectrum data from the spectrum analyzer (5-1), time domain pulse sequence data from the oscilloscope (6-1), and spatial spot distribution data from the CCD camera (7-1); (5) The collected data is fed back to the PC control subsystem, and the control parameters are generated through the neural network. Based on the genetic algorithm, closed-loop adjustment is performed: the output power of the pump source (3-1), the polarization adjustment amount of the first electronic polarization controller (4-1-1), the second electronic polarization controller (4-1-2), and the third electronic polarization controller (4-2) until time domain pulse sequence locking and spatial mode locking are achieved.

8. The method for generating a 2-micron multimode fiber laser seed source for space communication according to claim 7, characterized in that: In step (5): The neural network is a multi-layer perceptron architecture, and the input layer includes time domain pulse width, spectral center wavelength, and mode purity characteristic parameters; The fitness function of the genetic algorithm comprehensively evaluates the temporal stability, spectral matching and spatial pattern similarity indicators.

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