Wavefront correction system and method for offshore quantum key distribution system

Abstract

The invention discloses a wavefront correction system and method for an offshore quantum key distribution system, and relates to the technical field of wavefront correction, and the system comprises a laser, a transmission light path, a redundant light optical antenna, at least three local oscillator light optical antennas, a signal preprocessing module and a wavefront correction module. The laser generates an initial optical signal; the transmission optical path divides the initial optical signal into a local oscillator optical signal and a redundant optical signal, and transmits the local oscillator optical signal, the redundant optical signal and an echo signal; the local oscillator optical antenna transmits a local oscillator optical signal and receives a local oscillator echo signal in a corresponding direction; the redundant light optical antenna transmits a redundant light signal and receives a redundant echo signal in a corresponding direction; the signal preprocessing module preprocesses and corrects the local oscillator echo signal and the redundant echo signal to obtain a target beam signal; and the wavefront correction module calculates a real-time atmospheric turbulence value according to the target beam signal to carry out wavefront correction. The three-dimensional velocity vector component of the carrier can be measured at the same time.

Description

Technical Field

[0001] The present application relates to the technical field of wavefront correction, and more specifically, to a wavefront correction system and method for a maritime quantum key distribution system. Background Art

[0002] A maritime quantum key distribution (QKD) system is a system that uses the principles of quantum mechanics to perform secure key distribution at sea. With the continuous development of quantum communication technology, a maritime QKD system can also be combined with other quantum communication technologies, such as quantum satellite communication, quantum relay, etc., to achieve a wider and more efficient secure communication network.

[0003] Existing maritime quantum key distribution systems mainly rely on the quantum no-cloning theorem and the uncertainty of quantum measurement. The system transmits quantum states (such as photons) through a quantum channel and uses the encoding of quantum states to generate keys. The receiving party measures the received quantum states and compares them with the sending party to detect whether there are potential eavesdropping behaviors. If the channel is secure, both parties can continue to extract the shared key for subsequent secure communication.

[0004] However, currently, due to the complex atmospheric climate over the ocean, a maritime quantum key distribution (QKD) system can only operate under meteorological conditions of clear and windless weather. If the weather is slightly worse, it cannot operate, which greatly affects the usage conditions of the system. During the quantum key distribution process, it will be affected by atmospheric turbulence, resulting in out-of-sync transceiver systems. Moreover, the incorrect and scrambled codes caused by the phase change of the light source directly affect the coding rate of the system and greatly increase the error rate of the system. Summary of the Invention

[0005] In view of at least one defect or improvement requirement of the prior art, the present invention provides a wavefront correction system and method for a maritime quantum key distribution system, which are used to solve the problems in the prior art that due to the complex atmospheric climate over the ocean, the maritime quantum key distribution system is easily affected by atmospheric turbulence, increasing the error rate of the system and can only operate under meteorological conditions of clear and windless weather.

[0006] To achieve the above object, according to the first aspect of the present invention, there is provided a wavefront correction system for a maritime quantum key distribution system, including: a laser, a transmission optical path, a redundant optical antenna, at least three local oscillator optical antennas, a signal preprocessing module, and a wavefront correction module; the transmission optical path is respectively connected to the laser, the redundant optical antenna, the local oscillator optical antennas, and the signal preprocessing module; the signal preprocessing module is further connected to the wavefront correction module;

[0007] wherein, the laser is used to generate an initial optical signal;

[0008] The transmission optical path is used to divide the initial optical signal into a local oscillator optical signal and a redundant optical signal, and transmit the local oscillator optical signal, the redundant optical signal, and the echo signal;

[0009] The local oscillator optical antenna is used to transmit the local oscillator optical signal and receive the local oscillator echo signal in the corresponding direction;

[0010] The redundant optical antenna is used to transmit the redundant optical signal and receive the redundant echo signal in the corresponding direction;

[0011] The signal preprocessing module is used to preprocess and correct the local oscillator echo signal and the redundant echo signal to obtain the target beam signal;

[0012] The wavefront correction module is used to calculate the real-time atmospheric turbulence value according to the target beam signal and perform wavefront correction according to the real-time atmospheric turbulence value.

[0013] In a possible implementation, the transmission optical path further includes: a light ray emission optical path and a light ray echo optical path; the light ray emission optical path is respectively connected to the local oscillator optical antenna and the redundant optical antenna, and the light ray echo optical path is respectively connected to the local oscillator optical antenna and the redundant optical antenna;

[0014] Among them, the light ray emission optical path is used to divide the initial optical signal into a local oscillator optical signal and a redundant optical signal, and transmit the local oscillator optical signal to the local oscillator optical antenna and the redundant optical signal to the redundant optical antenna;

[0015] The light ray echo optical path is used to convert the local oscillator echo signal and the redundant echo signal into electrical signals and transmit them to the signal preprocessing module.

[0016] In a possible implementation, the light ray emission optical path includes a plurality of isolators and a plurality of couplers; the isolators and the couplers are connected in an alternating manner;

[0017] Among them, the isolator is used to prevent the initial optical signal and the local oscillator optical signal from propagating in the reverse direction;

[0018] The coupler is used to split the initial optical signal and the local oscillator optical signal, or combine the initial optical signal and the local oscillator optical signal.

[0019] In a possible implementation, the light ray echo optical path includes a circulator, an amplifier, and a detector; the circulator, the amplifier, and the detector are connected in sequence;

[0020] Among them, the circulator is used to transmit the local oscillator echo signal and the redundant echo signal along a specific optical path;

[0021] The amplifier is used to amplify the local oscillator echo signal and enhance the power of the local oscillator echo signal;

[0022] The detector is used to convert the local oscillator echo signal and the redundant echo signal into the local oscillator echo electrical signal and the redundant echo electrical signal.

[0023] In a possible implementation, the wavefront correction module includes a field programmable gate array and a digital signal processor, and the field programmable gate array is connected to the digital signal processor;

[0024] Among them, the field programmable gate array is used to adjust the acquisition frequency and acquire the digital signal of the target beam signal;

[0025] The digital signal processor is used to calculate the three-dimensional velocity vector components of the vehicle to be speed-measured according to the digital signal, and calculate the real-time atmospheric turbulence value according to the three-dimensional velocity vector components for wavefront correction.

[0026] In a possible implementation, the laser is a narrow-linewidth semiconductor laser with a wavelength of 1.55 μm and a power of 12 mW.

[0027] According to the second aspect of the present invention, there is also provided a wavefront correction method for a marine quantum key distribution system, based on the wavefront correction system for a marine quantum key distribution system according to any one of the above possible implementations, including:

[0028] Establish a horizontal space coordinate system based on the moving direction of the vehicle to be speed-measured, and establish an antenna space coordinate system based on the target beam signal;

[0029] When the horizontal space coordinate system coincides with the antenna space coordinate system, calculate the three-dimensional velocity vector components of the vehicle to be speed-measured on the antenna space coordinate system according to the target beam signal and the antenna space coordinate system;

[0030] When the horizontal space coordinate system does not coincide with the antenna space coordinate system, determine the coordinate transformation matrix according to the rotation angle between the antenna space coordinate system and the horizontal space coordinate system, and convert the three-dimensional velocity vector components on the antenna space coordinate system into the three-dimensional velocity vector components on the horizontal space coordinate system based on the coordinate transformation matrix;

[0031] Calculate the real-time atmospheric turbulence value according to the three-dimensional velocity vector components on the horizontal space coordinate system for wavefront correction.

[0032] In a possible implementation, when the horizontal space coordinate system coincides with the antenna space coordinate system, calculating the three-dimensional velocity vector components of the vehicle to be speed-measured on the antenna space coordinate system according to the local oscillator echo signal and the antenna space coordinate system includes:

[0033] Determine the beam unit vector vector in the antenna space coordinate system according to the target beam signal, and inversely calculate the carrier velocity vector of the vehicle to be speed-measured;

[0034] Calculate the first included angle between the target beam signal and each coordinate axis of the antenna space coordinate system according to the beam unit vector vector;

[0035] Based on the beam unit vector vector, the carrier velocity vector, and the first included angle, calculate the three-dimensional velocity vector components of the carrier to be measured on the antenna space coordinate system.

[0036] In a possible implementation manner, calculating the first included angle between the target beam signal and each coordinate axis of the antenna space coordinate system according to the beam unit vector vector further includes:

[0037] Calculate the included angle between the beam unit vector vector and the first coordinate axis of the antenna space coordinate system according to the beam unit vector vector;

[0038] Project the beam unit vector vector onto the first preset plane, and calculate the included angle between the projection and the second coordinate axis;

[0039] Based on the trigonometric relationship, the included angle between the beam unit vector vector and the first coordinate axis of the antenna space coordinate system, and the included angle between the projection and the second coordinate axis, calculate the included angles between the beam unit vector vector and the second coordinate axis and the third coordinate axis of the antenna space coordinate system respectively.

[0040] In a possible implementation manner, when the horizontal space coordinate system does not coincide with the antenna space coordinate system, determine the coordinate transformation matrix according to the rotation angle between the antenna space coordinate system and the horizontal space coordinate system, and based on the coordinate transformation matrix, convert the three-dimensional velocity vector components on the antenna space coordinate system into the three-dimensional velocity vector components on the horizontal space coordinate system, including:

[0041] Based on the attitude change of the carrier to be measured, determine the pitch angle of the carrier to be measured in the horizontal space coordinate system and the roll angle in the antenna space coordinate system;

[0042] Calculate the coordinate transformation matrix between the horizontal space coordinate system and the antenna space coordinate system according to the pitch angle and the roll angle;

[0043] Based on the coordinate transformation matrix, convert the three-dimensional velocity vector components on the antenna space coordinate system into the three-dimensional velocity vector components on the horizontal space coordinate system.

[0044] Generally speaking, compared with the prior art through the above technical solutions conceived by the present invention, the following beneficial effects can be achieved:

[0045] A wavefront correction system for a maritime quantum key distribution system provided by the present invention transmits and receives signals through at least three local oscillator optical antennas, can simultaneously measure the three-dimensional velocity vector components of a carrier, and can thus accurately calculate the real-time atmospheric turbulence value, which is beneficial for wavefront correction. Through the configuration of multiple optical antennas and redundant optical signals, the influence of attitude changes such as the jolting and swaying of the carrier on the velocity measurement result can be effectively offset, ensuring accurate velocity measurement even under complex motion states, and thus guaranteeing the accurate calculation of the real-time atmospheric turbulence value. The atmospheric attenuation coefficient is measured in real time through redundant optical signals, and a control signal is generated to compensate and amplify the echo signal, ensuring that the system can respond to environmental changes in real time and maintain the accuracy of the real-time atmospheric turbulence value calculation. By transmitting and receiving redundant optical signals through redundant optical antennas, the system can correct in real time the influence of atmospheric attenuation and other environmental factors on the velocity measurement accuracy, ensuring high accuracy of the velocity measurement result. The redundant optical signals measure the attenuation coefficient through an optical power meter, correct the attenuation of the local oscillator optical signal in real time, improve the environmental adaptability and reliability of the system, and reduce the influence of atmospheric turbulence. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings required in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0047] Figure 1 Schematic structural diagram of an embodiment of a wavefront correction system for a maritime quantum key distribution system provided by the present invention;

[0048] Figure 2 Schematic flowchart of an embodiment of a wavefront correction method for a maritime quantum key distribution system provided by the present invention;

[0049] Figure 3 provided by the present invention Figure 2 Schematic flowchart of an embodiment of step S202 in

[0050] Figure 4 provided by the present invention Figure 3 Schematic flowchart of an embodiment of step S302 in

[0051] Figure 5 provided by the present invention Figure 2 Schematic flowchart of an embodiment of step S203 in

[0052] Figure 6 Spatial schematic diagram of an embodiment of a three-signal light beam configuration provided by the present invention;

[0053] Figure 7 Spatial schematic diagram of speed demodulation when the carrier attitude changes according to an embodiment provided by the present invention. Detailed implementation manners

[0054] In order to make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0055] The terms "first", "second", "third", etc. in the description and claims of this application and the above-mentioned drawings are used to distinguish different objects, rather than to describe a specific order. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device that includes a series of steps or units is not limited to the listed steps or units, but optionally further includes steps or units not listed, or optionally further includes other steps or units inherent to these processes, methods, products or devices.

[0056] The present invention provides a wavefront correction system and method for a marine quantum key distribution system, which will be described separately below.

[0057] Please refer to Figure 1 , Figure 1 which is a structural schematic diagram of an embodiment of the wavefront correction system for a marine quantum key distribution system provided by the present invention. In a specific embodiment of the present invention, a wavefront correction system for a marine quantum key distribution system is disclosed, including: a laser, a transmission optical path, a redundant optical antenna, at least three local oscillator optical antennas, a signal preprocessing module, and a wavefront correction module; the transmission optical path is respectively connected to the laser, the redundant optical antenna, the local oscillator optical antenna, and the signal preprocessing module; the signal preprocessing module is further connected to the wavefront correction module;

[0058] Among them, the laser 10 is used to generate an initial optical signal;

[0059] The transmission optical path is used to divide the initial optical signal into a local oscillator optical signal and a redundant optical signal, and transmit the local oscillator optical signal, the redundant optical signal, and the echo signal;

[0060] The local oscillator optical antenna is used to transmit the local oscillator optical signal and receive the local oscillator echo signal in the corresponding direction;

[0061] The redundant optical antenna is used to transmit the redundant optical signal and receive the redundant echo signal in the corresponding direction;

[0062] The signal preprocessing module 51 is used to preprocess and correct the local oscillator echo signal and the redundant echo signal to obtain the target beam signal;

[0063] The wavefront correction module 52 is used to calculate the real-time atmospheric turbulence value according to the target beam signal and perform wavefront correction according to the real-time atmospheric turbulence value.

[0064] In the above embodiment, the laser is the core light source of the system and is used to generate the initial optical signal. The laser usually adopts a narrow linewidth semiconductor laser, and the wavelength is selected in the 1.55 μm band. This band is not only harmless to the human eye, but also has a low attenuation rate in atmospheric transmission, which is suitable for long-distance transmission and high-precision speed measurement applications. The initial optical signal generated by the laser has high coherence and stability, providing a reliable light source for subsequent Doppler frequency shift measurement.

[0065] The transmission optical path ( Figure 1 not shown) is responsible for splitting and transmitting the initial optical signal generated by the laser. The transmission optical path usually includes a plurality of couplers and isolators, which are used to divide the initial optical signal into the local oscillator optical signal and the redundant optical signal. The local oscillator optical signal is used to measure the speed of the carrier, while the redundant optical signal is used to correct the influence of atmospheric attenuation and other environmental factors on the speed measurement accuracy. The transmission optical path is also responsible for transmitting the echo signal (i.e., the optical signal reflected from the target) to the signal preprocessing module for further processing.

[0066] The redundant optical antenna (such as Figure 1 the fourth optical antenna 34 in) is used to transmit the redundant optical signal and receive the redundant echo signal in the corresponding direction. The main function of the redundant optical signal is to correct the attenuation of the local oscillator optical signal in real time by measuring the atmospheric attenuation coefficient, thereby improving the accuracy and reliability of the speed measurement system. The redundant optical antenna is usually installed on the central axis of a plurality of local oscillator optical antennas to ensure that it can cover the entire speed measurement area and provide effective correction information under complex meteorological conditions.

[0067] This system includes at least three local oscillator optical antennas (such as Figure 1 the first optical antenna 31, the second optical antenna 32, and the third optical antenna 33 in), and each optical antenna is responsible for transmitting the local oscillator optical signal and receiving the local oscillator echo signal in the corresponding direction. The layout of the local oscillator optical antennas usually adopts a non-coplanar configuration to ensure that the three-dimensional velocity components (horizontal forward velocity, horizontal lateral velocity, and vertical velocity) of the carrier can be measured simultaneously. Through the collaborative work of multiple optical antennas, the system can accurately measure the speed under complex motion states such as the carrier bumping and shaking.

[0068] The signal preprocessing module is responsible for preprocessing and correcting the local oscillator echo signal and the redundant echo signal. The preprocessing process includes operations such as signal amplification, filtering, and analog-to-digital conversion to improve the signal-to-noise ratio and stability of the signal. The attenuation coefficient of the redundant echo signal is measured by an optical power meter, and a control signal is generated to compensate and amplify the local oscillator echo signal to ensure that the system can correct the influence of atmospheric attenuation and other environmental factors in real time. The preprocessed signal is transmitted to the wavefront correction module for further processing.

[0069] Based on the preprocessed target beam signal, the wavefront correction module calculates the three-dimensional velocity vector components of the vehicle to be measured for velocity (hereinafter referred to as the vehicle for short), calculates the real-time atmospheric turbulence value according to the calculated three-dimensional velocity vector components, and then performs wavefront correction according to the real-time atmospheric turbulence value. This module extracts the frequency information in the echo signal through the Doppler frequency shift detection algorithm, and combines the measurement results of multiple optical antennas to invert the three-dimensional velocity of the vehicle to calculate the real-time atmospheric turbulence value. The wavefront correction module usually uses digital signal processing technologies such as fast Fourier transform (FFT) and autocorrelation algorithm to improve the velocity measurement accuracy and real-time performance.

[0070] The working process of the system is as follows: The laser generates an initial optical signal, and the transmission optical path divides the initial optical signal into a local oscillator optical signal and a redundant optical signal. The local oscillator optical signal is transmitted to the target area through multiple local oscillator optical antennas and receives the echo signal; the redundant optical signal is transmitted through the redundant optical antenna and receives the echo signal. After being amplified, filtered, and corrected by the signal preprocessing module, the echo signal is transmitted to the wavefront correction module. The wavefront correction module calculates the three-dimensional velocity vector components of the vehicle through the Doppler frequency shift detection algorithm, further calculates the real-time atmospheric turbulence value, and then realizes wavefront correction based on technologies such as predictive control of the turbulence statistical model, multi-aperture and tomography technology, data-driven and machine learning, and information utilization of the turbulent channel.

[0071] Compared with the prior art, a wavefront correction system for a marine quantum key distribution system provided in this embodiment can transmit and receive signals through at least three local oscillator optical antennas, and can simultaneously measure the three-dimensional velocity vector components of the carrier, and then can accurately calculate the real-time atmospheric turbulence value, which is beneficial for wavefront correction. Through the configuration of multiple optical antennas and redundant optical signals, the influence of attitude changes such as the carrier's bumping and shaking on the speed measurement result can be effectively offset, ensuring that the speed can still be accurately measured under complex motion states, and thus ensuring the accurate calculation of the real-time atmospheric turbulence value. The redundant optical signals are used to measure the atmospheric attenuation coefficient in real time and generate control signals to compensate and amplify the echo signals, ensuring that the system can respond to environmental changes in real time and maintain the accuracy of the real-time atmospheric turbulence value calculation. By transmitting and receiving redundant optical signals through redundant optical antennas, the system can correct the influence of atmospheric attenuation and other environmental factors on the speed measurement accuracy in real time, ensuring the high accuracy of the speed measurement result. The redundant optical signals measure the attenuation coefficient through an optical power meter and correct the attenuation of the local oscillator optical signal in real time, improving the environmental adaptability and reliability of the system and reducing the influence of atmospheric turbulence.

[0072] In some embodiments of the present invention, the transmission optical path further includes: a light emission optical path and a light return optical path; the light emission optical path is respectively connected to the local oscillator optical antenna and the redundant optical antenna, and the light return optical path is respectively connected to the local oscillator optical antenna and the redundant optical antenna;

[0073] Among them, the light emission optical path is used to divide the initial optical signal into a local oscillator optical signal and a redundant optical signal, and transmit the local oscillator optical signal to the local oscillator optical antenna and the redundant optical signal to the redundant optical antenna;

[0074] The light return optical path is used to convert the local oscillator echo signal and the redundant echo signal into electrical signals and transmit them to the signal preprocessing module.

[0075] In the above embodiment, the main function of the light emission optical path ( Figure 1 not shown) is to split the initial optical signal generated by the laser and transmit it to the corresponding optical antenna. Specifically, the light emission optical path divides the initial optical signal into two parts: a local oscillator optical signal and a redundant optical signal.

[0076] The local oscillator optical signal is transmitted to the local oscillator optical antenna through the light emission optical path. As a preferred embodiment, at least three local oscillator optical antennas in the present invention are provided, which respectively emit local oscillator optical signals in different directions for measuring the three-dimensional velocity components of the carrier (horizontal forward velocity, horizontal lateral velocity, and vertical velocity). The redundant optical signal is transmitted to the redundant optical antenna through the light emission optical path. The main function of the redundant optical signal is to correct the attenuation of the local oscillator optical signal in real time by measuring the atmospheric attenuation coefficient, thereby improving the accuracy and reliability of the speed measurement system.

[0077] In some embodiments of the present invention, the optical emission path includes a plurality of isolators and a plurality of couplers; the isolators and the couplers are connected alternately;

[0078] Among them, the isolator is used to prevent the initial optical signal and the local oscillator optical signal from propagating in the reverse direction;

[0079] The coupler is used to split the initial optical signal and the local oscillator optical signal, or to combine the initial optical signal and the local oscillator optical signal.

[0080] In the above embodiments, in the optical emission path, the isolator is used to prevent the initial optical signal or the local oscillator optical signal from being reflected back to the laser or other optical elements, avoiding interference to the system caused by the reflected light. The reflected light may affect the stability of the laser and even damage the laser. Therefore, the isolator plays an important protective role in the system. By preventing the reverse propagation of the reflected light, the isolator ensures the unidirectional transmission of the optical signal, reduces the noise and interference in the system, and thus improves the stability and speed measurement accuracy of the system.

[0081] The coupler distributes the initial optical signal to different optical paths according to a certain splitting ratio (such as 90:10 or 1:1:1), ensuring that the power of the local oscillator optical signal and the redundant optical signal meets the system design requirements. In some cases, the coupler can also be used to combine multiple optical signals. In some configurations of the system, the coupler can combine multiple local oscillator optical signals into one signal for subsequent processing or transmission.

[0082] In the optical emission path, the isolator and the coupler work together in an alternating connection manner. Specifically, the isolator is usually located between the couplers, ensuring that the optical signal in each section of the optical path can be transmitted unidirectionally and preventing interference from the reflected light.

[0083] Through the precise splitting of the coupler, the system can distribute the initial optical signal to different optical paths according to the design requirements, ensuring that the power ratio of the local oscillator optical signal and the redundant optical signal meets the system requirements. The introduction of the isolator effectively prevents the reverse propagation of the optical signal, reduces the noise and interference in the system, and improves the stability and speed measurement accuracy of the system. The alternating connection of the isolator and the coupler makes the optical emission path have a modular feature, facilitating the debugging and maintenance of the system.

[0084] In some embodiments of the present invention, the optical return path includes a circulator, an amplifier, and a detector; the circulator, the amplifier, and the detector are connected in sequence;

[0085] Among them, the circulator is used to transmit the local oscillator echo signal and the redundant echo signal according to a special optical path;

[0086] The amplifier is used to amplify the local oscillator echo signal and enhance the power of the local oscillator echo signal;

[0087] The detector is used to convert the local oscillator echo signal and the redundant echo signal into the local oscillator echo electrical signal and the redundant echo electrical signal.

[0088] In the above embodiment, the circulator (such as Figure 1 Cir1, 2, 3, 4 in Figure 1 ) is a multi-port optical device that can direct the optical signal to be transmitted along a specific optical path. In the optical return echo optical path ( Figure 1 not shown), the circulator is used to receive the local oscillator echo signal and the redundant echo signal from the optical antenna and transmit them to the amplifier and the detector along a specific optical path. The design of the circulator ensures the unidirectional transmission of the optical signal, preventing the echo signal from reflecting back to the optical antenna or other optical components and avoiding interfering with the normal operation of the system. The local oscillator echo signal and the redundant echo signal can be transmitted to different amplifiers or detectors through the circulator respectively, ensuring that each signal can be processed independently and avoiding crosstalk between signals.

[0089] The amplifier (such as Figure 1 EDFA1, 2 in Figure 1 ) is used to amplify the local oscillator echo signal and enhance the power of the echo signal. Since the echo signal will be affected by atmospheric attenuation, scattering, etc. during transmission, the signal power may be significantly reduced. The amplifier boosts the power of the echo signal to a level suitable for subsequent processing through gain control, ensuring that information is not lost due to too low signal power during transmission and detection. The amplifier can also expand the dynamic range of the system, enabling it to process echo signals of different intensities. In a complex ocean environment, the intensity of the echo signal may fluctuate significantly due to factors such as sea surface waves and target distance. The amplifier ensures that the system can adapt to signal inputs of different intensities through technologies such as automatic gain control (AGC).

[0090] The detector is a key component in the optical return echo optical path and is responsible for converting the optical signal into an electrical signal. Specifically, the detector converts the local oscillator echo signal and the redundant echo signal into the local oscillator echo electrical signal and the redundant echo electrical signal, facilitating subsequent signal processing and analysis. The optoelectronic conversion process is usually based on the photoelectric effect. The detector converts the photon energy of the optical signal into the electrical energy of the electrical signal, outputting a voltage or current signal proportional to the intensity of the optical signal. The detector usually also has certain signal conditioning functions, such as low-noise amplification and filtering, to ensure that the converted electrical signal has a high signal-to-noise ratio, which helps to reduce the velocity measurement error.

[0091] Through the directional transmission function of the circulator, the optical return wave path can efficiently transmit the echo signal from the optical antenna to the amplifier and detector, ensuring the integrity and real-time nature of the signal. The amplifier ensures that the echo signal does not lose information due to too low power during transmission through gain control and dynamic range extension; the detector ensures that the converted electrical signal has a high signal-to-noise ratio through photoelectric conversion and signal conditioning, facilitating subsequent processing. The sequential connection of the circulator, amplifier, and detector makes the optical return wave path modular, facilitating system debugging and maintenance.

[0092] In Figure 1 it, the transmission optical path includes the first coupler 21, the second coupler 22, the third coupler 23, the fourth coupler 24, the fifth coupler 25, the sixth coupler 26, and the seventh coupler 27, the first isolator 71 and the second isolator 72, the circulators Cir1, 2, 3, 4, the amplifiers EDFA1, 2, the first detector 81, the second detector 82, the third detector 83, the fourth detector 84, and the first optical power meter 61, the second optical power meter 62.

[0093] The first coupler 21 is used to divide the initial optical signal output by the laser 10 into two paths, one path is output to the second coupler 22, and the other path is output to the fourth coupler 24.

[0094] In this embodiment, the splitting ratio of the first coupler 21 is 90:10. Among them, the initial optical signal with a splitting ratio of 90 is output to the second coupler 22, and the initial optical signal with a splitting ratio of 10 is output to the fourth coupler 24. Since the initial optical signal output to the fourth coupler 24 is used as the local oscillator optical signal, and the one output to the second coupler 22 is used as the redundant optical signal. Considering that the redundant optical signal may be damaged during atmospheric transmission, therefore, the larger the splitting ratio of the redundant optical signal is set, the better the speed measurement effect is, and at the same time, the splitting ratio of the local oscillator optical signal cannot be too weak.

[0095] In some embodiments of the present invention, the wavefront correction module includes a field programmable gate array and a digital signal processor, and the field programmable gate array and the digital signal processor are connected;

[0096] Among them, the field programmable gate array is used to adjust the acquisition frequency and acquire the digital signal of the target beam signal;

[0097] The digital signal processor is used to calculate the three-dimensional velocity vector components of the vehicle to be measured according to the digital signal, and calculate the real-time atmospheric turbulence value according to the three-dimensional velocity vector components for wavefront correction.

[0098] In the above embodiments, if a separate digital signal processor (DSP) or field-programmable gate array (FPGA) is used to complete the logic control and data processing of the system, high requirements will be imposed on both the resources and performance of the chip. With the development of DSPs and FPGAs, general mainstream DSPs can already meet the requirements for processing speed, processing accuracy, etc. of complex algorithms. However, traditional DSPs adopt the Harvard architecture, which is essentially sequential in execution. For algorithms with high requirements for processing speed and relatively simple structures, the FPGA with parallel execution is significantly superior to the DSP in terms of efficiency. In addition, the FPGA chip has very strong logic control capabilities. Therefore, the system adopting the DSP+FPGA structure in the present invention combines the respective advantages of DSPs and FPGAs, taking both speed and flexibility into account.

[0099] Since it is necessary to simultaneously collect and process three signals, considering the hardware structure, program design, and real-time performance of the system, the system adopts a multi-channel single-core architecture. Therefore, the entire hardware system adopts a multi-channel single-core electrical signal processing solution based on a field-programmable gate array (FPGA) + digital signal processor (DSP). The voltage signals output by the photodetector are amplified, low-pass filtered and other signal conditioning, and then are sampled at high speed by three A / D conversion circuits respectively, and the converted digital signals are output in parallel to the FPGA for buffering and preprocessing. When the FPGA completes the preprocessing of the digital signal, it sends an interrupt signal to the DSP to notify the DSP to read the output result of the FPGA, and at the same time waits for the final result of the signal processing returned by the DSP. After responding to the interrupt, the DSP reads the preprocessed signal from the FPGA and performs signal processing, and then feeds back the final result to the FPGA on the one hand. The FPGA uses this returned signal to set the sampling clock for the next moment and control the A / D sampling rate. On the other hand, the measurement result is output through the serial port.

[0100] In some embodiments of the present invention, the laser is a narrow-linewidth semiconductor laser with a wavelength of 1.55 μm and a power of 12 mW.

[0101] In the above embodiments, the selection of the wavelength of 1.55 μm is based on the low attenuation characteristics of this band in the atmosphere and the consideration of the safety of the human eye, while the narrow linewidth helps to reduce the Doppler frequency shift error during the measurement process and improve the speed measurement accuracy. The power of 12 mW not only ensures sufficient signal strength but also avoids potential hazards to the surrounding environment.

[0102] Please refer to Figure 2 , Figure 2The flowchart of an embodiment of the wavefront correction method for a maritime quantum key distribution system provided by the present invention. According to the second aspect of the present invention, a wavefront correction method for a maritime quantum key distribution system is further provided. Based on the wavefront correction system for a maritime quantum key distribution system in any of the above possible implementation manners, it includes:

[0103] S201. Establish a horizontal space coordinate system based on the moving direction of the vehicle to be measured for speed, and establish an antenna space coordinate system based on the target beam signal;

[0104] S202. When the horizontal space coordinate system coincides with the antenna space coordinate system, calculate the three-dimensional velocity vector components of the vehicle to be measured for speed on the antenna space coordinate system according to the target beam signal and the antenna space coordinate system;

[0105] S203. When the horizontal space coordinate system does not coincide with the antenna space coordinate system, determine the coordinate transformation matrix according to the rotation angle between the antenna space coordinate system and the horizontal space coordinate system, and convert the three-dimensional velocity vector components on the antenna space coordinate system into the three-dimensional velocity vector components on the horizontal space coordinate system based on the coordinate transformation matrix;

[0106] S204. Calculate the real-time atmospheric turbulence value according to the three-dimensional velocity vector components on the horizontal space coordinate system for wavefront correction.

[0107] In the above embodiment, based on the moving direction of the vehicle to be measured for speed, a horizontal space coordinate system is first established. This coordinate system is used to describe the motion state of the vehicle on the horizontal plane, usually including the forward direction, the lateral direction, and the vertically upward direction. At the same time, according to the laser beam signal emitted in the speed measurement system, an antenna space coordinate system is established. The antenna space coordinate system is closely related to the emission direction of the laser beam and is used to directly measure the Doppler frequency shift after the beam is scattered by the sea surface and returns.

[0108] When the vehicle is in the rated state, that is, when the horizontal space coordinate system coincides with the antenna space coordinate system, the three-dimensional velocity vector components of the vehicle to be measured for speed on the antenna space coordinate system can be directly obtained according to the relationship between the received target beam signal (i.e., the scattered echo of the laser beam by the sea surface) and the antenna space coordinate system through the calculation of the Doppler frequency shift. These components represent the velocity projections of the vehicle in the beam pointing direction.

[0109] When the attitude of the carrier changes during actual navigation, such as jolting or swaying, resulting in the non - coincidence of the horizontal space coordinate system and the antenna space coordinate system, it is necessary to first determine the rotation angle between these two coordinate systems. The rotation angle can be accurately measured by sensors installed on the carrier, such as fiber optic gyroscopes, etc. Based on the measured rotation angle, a coordinate transformation matrix is constructed. This matrix is used to convert the three - dimensional velocity vector components measured in the antenna space coordinate system into the three - dimensional velocity vector components in the horizontal space coordinate system, taking into account the attitude change of the carrier, ensuring the accuracy and practicality of the velocity measurement result.

[0110] Please refer to Figure 3 , Figure 3 which is provided by the present invention Figure 2 is a schematic flowchart of an embodiment of step S202 in. In some embodiments of the present invention, when the horizontal space coordinate system coincides with the antenna space coordinate system, according to the local oscillator echo signal and the antenna space coordinate system, calculate the three - dimensional velocity vector components of the vehicle to be speed - measured in the antenna space coordinate system, including:

[0111] S301. Determine the beam unit vector vector in the antenna space coordinate system according to the target beam signal, and inversely calculate the vehicle velocity vector of the vehicle to be speed - measured;

[0112] S302. Calculate the first included angles between the target beam signal and the respective coordinate axes of the antenna space coordinate system according to the beam unit vector vector;

[0113] S303. Calculate the three - dimensional velocity vector components of the vehicle to be speed - measured in the antenna space coordinate system based on the beam unit vector vector, the vehicle velocity vector, and the first included angles.

[0114] In the above - mentioned embodiment, using the laser Doppler effect, by measuring the Doppler frequency shift to determine the characteristics of the target beam signal, and then combining the installation angle of the antenna and the emission wavelength, the beam unit vector vector can be calculated. This vector describes the direction of the beam in the antenna space coordinate system. Then, using this beam unit vector vector and combining the measurement result of the Doppler frequency shift, through a series of mathematical operations, the velocity vector of the vehicle to be speed - measured is inversely calculated (the inverse process can be realized by existing technologies, and the present invention will not elaborate too much on this).

[0115] Calculate the first included angles between the target beam signal and the respective coordinate axes of the antenna space coordinate system according to the beam unit vector vector. After determining the beam unit vector vector, the included angles between it and the X - axis, Y - axis, and Z - axis of the antenna space coordinate system can be calculated, providing important information about the beam direction and being a key parameter for subsequent calculation of the three - dimensional velocity vector components.

[0116] Calculate the three-dimensional velocity vector components of the vehicle to be speed-measured in the antenna space coordinate system based on the beam unit vector vector, the vehicle velocity vector, and the first angle. Using the beam unit vector vector, the vehicle velocity vector, and the first angle obtained previously, through vector operations, solve for the three-dimensional velocity vector components of the vehicle to be speed-measured in the antenna space coordinate system. These components respectively represent the magnitudes of the velocities of the vehicle in the X-axis, Y-axis, and Z-axis directions. Since the horizontal space coordinate system coincides with the antenna space coordinate system, therefore, at this time, the three-dimensional velocity vector components of the vehicle to be speed-measured in the antenna space coordinate system are also the three-dimensional velocity vector components in the horizontal space coordinate system.

[0117] Please refer to Figure 4 , Figure 4 provided by the present invention Figure 3 is a schematic flowchart of an embodiment of step S302 in

[0118] S401. Calculate the angle between the beam unit vector vector and the first coordinate axis of the antenna space coordinate system according to the beam unit vector vector;

[0119] S402. Project the beam unit vector vector onto the first preset plane and calculate the angle between the projection and the second coordinate axis;

[0120] S403. Calculate the angles between the beam unit vector vector and the second coordinate axis and the third coordinate axis of the antenna space coordinate system respectively based on the trigonometric relationship, the angle between the beam unit vector vector and the first coordinate axis of the antenna space coordinate system, and the angle between the projection and the second coordinate axis.

[0121] In the above embodiment, the cosine value of the angle is obtained through the dot product and modulus length calculation of vectors, and then the angle itself is obtained. Specifically, the ratio of the projection length of the beam unit vector vector on the first coordinate axis to its modulus length is the cosine value of the angle, and the angle can be obtained by using the inverse cosine function.

[0122] The first preset plane is the XOZ plane. The projection vector of the beam unit vector vector in this plane can be obtained through the vector projection formula. Then, using a method similar to S401, the angle between the projection vector and the second coordinate axis (i.e., the axis perpendicular to the first coordinate axis in this plane) can be calculated.

[0123] Using the trigonometric relationships in three-dimensional space, given the angle between the beam unit vector and the first coordinate axis and the angle between the projection of the beam unit vector and the second coordinate axis in a certain plane, the angles between the beam unit vector and the second and third coordinate axes can be deduced through the knowledge of spatial geometry. Specifically, the cross product and magnitude of vectors can be used to calculate the other two angles, or a spatial right triangle can be constructed and the Pythagorean theorem and the properties of trigonometric functions can be used to solve for the angles.

[0124] Please refer to Figure 5 , Figure 5 an embodiment provided by the present invention Figure 2 is a schematic flowchart of step S203 in an embodiment. In some embodiments of the present invention, when the horizontal space coordinate system does not coincide with the antenna space coordinate system, the coordinate transformation matrix is determined according to the rotation angle between the antenna space coordinate system and the horizontal space coordinate system, and the three-dimensional velocity vector components on the antenna space coordinate system are converted into the three-dimensional velocity vector components on the horizontal space coordinate system based on the coordinate transformation matrix, including:

[0125] S501. Determine the pitch angle of the speed-measuring carrier in the horizontal space coordinate system and the roll angle in the antenna space coordinate system based on the attitude change of the speed-measuring carrier;

[0126] S502. Calculate the coordinate transformation matrix between the horizontal space coordinate system and the antenna space coordinate system according to the pitch angle and the roll angle;

[0127] S503. Convert the three-dimensional velocity vector components on the antenna space coordinate system into the three-dimensional velocity vector components on the horizontal space coordinate system based on the coordinate transformation matrix.

[0128] In the above embodiment, based on the attitude change of the speed-measuring carrier, high-precision sensors such as fiber optic gyroscopes installed on the ship chassis are used to accurately measure the pitch angle of the speed-measuring carrier in the horizontal space coordinate system and the roll angle in the antenna space coordinate system. The changes in these two angles reflect the attitude change of the carrier in three-dimensional space.

[0129] According to the measured pitch angle and roll angle, the coordinate transformation matrix between the horizontal space coordinate system and the antenna space coordinate system is calculated using the principles of trigonometric relationships and rotation matrices. This matrix is the key to realizing the transformation between the two coordinate systems.

[0130] Using the calculated coordinate transformation matrix, the three-dimensional velocity vector components measured on the antenna space coordinate system are converted into the three-dimensional velocity vector components on the horizontal space coordinate system. In this way, no matter how the attitude of the carrier changes, the system can output accurate speed measurement results.

[0131] Please refer to Figure 6 , Figure 6Please refer to the spatial schematic diagram of an embodiment of the three-signal light beam configuration provided by the present invention. Figure 7 , Figure 7 Please refer to the spatial schematic diagram of an embodiment of the speed demodulation when the attitude of the carrier provided by the present invention. In a specific embodiment of the present invention, an antenna coordinate system O-XYZ and a horizontal coordinate system O-X r Y r Z r are established. Under the rated condition, the antenna coordinate system O-XYZ coincides with the horizontal coordinate system O-X r Y r Z r . The point O is the intersection of the reverse directions of the three beams. The X r axis is the forward direction of the carrier, the Z r axis is the lateral direction of the carrier, and the Y r axis is the vertically upward direction. The X r OZ r plane of the horizontal coordinate system is parallel to the horizontal plane where the carrier runs. Therefore, the horizontal coordinate system can be understood as the antenna coordinate system under the rated condition. However, when the attitude of the carrier changes, a certain rotation angle will appear between the antenna coordinate system and the horizontal coordinate system.

[0132] The laser beams are non-collinearly directed towards the ground. For beam i (i can be 1, 2, 3), the unit vector of the beam can be expressed as Then the coordinates in the O-XYZ coordinate system are:

[0133]

[0134] Where The angle between the projection of on the XOZ plane and the X axis is which is the azimuth angle; i The angle between and the negative half-axis of the Y axis is θ i , which is the zenith angle. Additionally, let The angle between i and the X axis is α i , i The angle between i and the Z axis is β . Then according to the trigonometric relationship, the relationships between α

[0135]

[0136] and θ

[0137]

[0138] Solving the system of equations shown above, the three components of the velocity vector in the horizontal coordinate system can be obtained as follows:

[0139]

[0140] where D = a 3 (b 1 c 2 -b 2 c 1 ) + a 2 (b 3 c 1 -b 1 c 3 ) + a 1 (b 2 c 3 -b 3 c 2 ).

[0141] In actual measurement, the attitude of the carrier may change at any time. When the carrier jolts and sways, the beam pointing angle will change accordingly. Therefore, when calculating the moving speed of the carrier in the horizontal coordinate system, the influence of attitude change needs to be considered. Here, the pitch angle and roll angle are used to characterize the degree of jolting and swaying of the carrier. Let the pitch angle of the carrier be the counterclockwise rotation angle P (pitch angle) around the Z r axis, and the roll angle be the counterclockwise rotation angle R (roll angle) around the X axis. The attitude change can be represented by the rotation matrix as follows:

[0142]

[0143] The pitch angle P and roll angle R can be accurately measured by the fiber optic gyro installed on the bottom of the ship. The inertial navigation system transmits the pitch angle and roll angle to the three-beam laser Doppler velocimeter in real time, and then the A PR matrix can be obtained. According to the following formula, the three-dimensional velocity of the carrier in the horizontal coordinate system under pitch and roll conditions can be inversely calculated:

[0144]

[0145] Expanding the above formula, we get:

[0146]

[0147] The output wind speed value is transmitted to the ITU-R model. The ITU-R model gives an empirical model from the surface layer to the atmospheric space to calculate the real-time atmospheric turbulence value:

[0148]

[0149] where v is the resultant velocity of the three-dimensional velocity of the carrier in the horizontal coordinate system, is the refractive index structure constant at sea level, generally 1.7×10-14m-2 / 3, and H represents the height from the sea surface, thus the real-time atmospheric turbulence value Cn can be obtained. 2 (H).

[0150] In a preferred embodiment of the present invention, the specific process of calculating the real-time atmospheric turbulence value based on the three-dimensional velocity vector components in the horizontal space coordinate system for wavefront correction is as follows:

[0151] (1) Predictive control based on the turbulence statistical model

[0152] Kolmogorov theory: Using the turbulence power spectrum model (such as Cn 2 Cn 2 structure constant) to optimize the control algorithm parameters and predict the spatio-temporal evolution of wavefront distortion.

[0153] Prediction algorithm: Combining the Kalman filter or the minimum mean square error (MMSE) method to adjust the corrector in advance and reduce the influence of system delay.

[0154] (2) Multi-aperture and tomography techniques

[0155] Multi-aperture system (such as multi-telescope array): By the difference in turbulence perturbations of different paths, combining the tomography algorithm to reconstruct the three-dimensional turbulence distribution and improve the correction accuracy.

[0156] Laser guide star (LGS): Using the "artificial star" generated by the high-altitude sodium layer or Rayleigh scattering as the reference light source to expand the correction field of view.

[0157] (3) Data-driven and machine learning

[0158] Deep learning model: Training a neural network to learn the turbulent dynamic characteristics from historical wavefront data to achieve real-time distortion prediction (such as using LSTM or convolutional network).

[0159] Reinforcement learning: Optimizing the correction strategy to reduce the dependence on the guide star (applicable to the scenario without reference star).

[0160] (4) Information utilization of the turbulent channel

[0161] Free space optical communication: By monitoring the signal fluctuation characteristics (such as the scintillation index) caused by turbulence, dynamically adjusting the wavefront at the transmitting end or the adaptive gain at the receiving end.

[0162] Scattered light multiplexing: Utilizing the turbulence scattering effect of multi-path transmission and combining MIMO technology to enhance the signal stability.

[0163] In summary, a wavefront correction system for a marine quantum key distribution system provided by the present invention can transmit and receive signals through at least three local oscillator optical antennas, and can simultaneously measure the three-dimensional velocity vector components of the carrier, and then can accurately calculate the real-time atmospheric turbulence value, which is beneficial to wavefront correction. Through the configuration of multiple optical antennas and redundant optical signals, the influence of attitude changes such as the jolting and shaking of the carrier on the velocity measurement result can be effectively offset, ensuring that the velocity can still be accurately measured under complex motion states, and thus ensuring the accurate calculation of the real-time atmospheric turbulence value. The atmospheric attenuation coefficient is measured in real time through redundant optical signals, and a control signal is generated to compensate and amplify the echo signal, ensuring that the system can respond to environmental changes in real time and maintain the accuracy of the real-time atmospheric turbulence value calculation. By transmitting and receiving redundant optical signals through redundant optical antennas, the system can correct the influence of atmospheric attenuation and other environmental factors on the velocity measurement accuracy in real time, ensuring the high accuracy of the velocity measurement result. The redundant optical signal measures the attenuation coefficient through a optical power meter, corrects the attenuation of the local oscillator optical signal in real time, improves the environmental adaptability and reliability of the system, and reduces the influence of atmospheric turbulence.

[0164] The present application also provides a computer-readable storage medium, on which a computer program is stored. When the program is executed by a processor, the steps of the above method are implemented. Among them, the computer-readable storage medium may include, but is not limited to, any type of disk, including floppy disks, optical disks, DVDs, CD-ROMs, microdrives, and magneto-optical disks, ROMs, RAMs, EPROMs, EEPROMs, DRAMs, VRAMs, flash memory devices, magnetic cards or optical cards, nano-systems (including molecular memory ICs), or any type of medium or device suitable for storing instructions and / or data.

[0165] It should be noted that, for the foregoing method embodiments, for the sake of simple description, they are all expressed as a series of action combinations. However, those skilled in the art should know that the present application is not limited by the described action sequence, because according to the present application, certain steps can be performed in other sequences or simultaneously. Secondly, those skilled in the art should also know that the embodiments described in the specification are all preferred embodiments, and the actions and modules involved are not necessarily essential to the present application.

[0166] In the above embodiments, the descriptions of the various embodiments have their own emphases. For the parts not detailed in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0167] In several embodiments provided in this application, it should be understood that the disclosed device can be implemented in other ways. For example, the device embodiments described above are merely illustrative. For example, the division of the units is only a logical function division. In actual implementation, there may be other division methods. For example, multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the displayed or discussed coupling or direct coupling or communication connection between each other can be through some service interfaces. The indirect coupling or communication connection of the device or unit can be in an electrical or other form.

[0168] The units described as separate components may or may not be physically separated. The components displayed as units may or may not be physical units, that is, they can be located in one place or distributed to multiple network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0169] In addition, in each embodiment of this application, the functional units can be integrated in a processing unit, or each unit can exist physically alone, or two or more units can be integrated in one unit. The above-mentioned integrated units can be implemented in the form of hardware or in the form of software functional units.

[0170] If the above-mentioned integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable memory. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, or all or part of this technical solution, can be embodied in the form of a software product. This computer software product is stored in a memory and includes several instructions to enable a computer device (which can be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the methods described in each embodiment of this application. And the aforementioned memory includes: USB flash drive, read-only memory (ROM), random access memory (RAM), mobile hard disk, magnetic disk, or optical disk, etc., which can store program codes.

[0171] Those of ordinary skill in the art can understand that all or part of the steps in the various methods of the above embodiments can be completed by instructing relevant hardware through a program. This program can be stored in a computer-readable memory. The memory can include: flash drive, read-only memory (ROM), random access memory (RAM), magnetic disk, or optical disk, etc.

[0172] The above are only exemplary embodiments of the present disclosure, and the scope of the present disclosure cannot be limited thereby. That is, any equivalent changes and modifications made in accordance with the teachings of the present disclosure still fall within the scope covered by the present disclosure. Those skilled in the art will readily conceive of other embodiments of the present disclosure after considering the specification and practicing the disclosure herein. This application is intended to cover any variations, uses, or adaptations of the present disclosure that follow the general principles of the present disclosure and include known common general knowledge or conventional technical means in the technical field not recorded in the present disclosure. The specification and examples are only regarded as exemplary, and the scope and spirit of the present disclosure are defined by the claims.

[0173] The technical features of the above embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the various technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope recorded in this specification.

[0174] Those skilled in the art can easily understand that the above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A wavefront correction system for a marine quantum key distribution system, characterized in that: include: A laser, a transmission optical path, a redundant optical antenna, at least three local oscillator optical antennas, a signal preprocessing module, and a wavefront correction module; The transmission optical path is respectively connected to the laser, the redundant optical antenna, the local oscillator optical antenna and the signal preprocessing module; the signal preprocessing module is also connected to the wavefront correction module; Wherein, the laser is used to generate an initial optical signal; The transmission optical path is used to divide the initial optical signal into a local oscillator optical signal and a redundant optical signal, and transmit the local oscillator optical signal, the redundant optical signal and the echo signal; The local oscillator optical antenna is used to transmit the local oscillator optical signal and receive the local oscillator echo signal in the corresponding direction; The redundant optical antenna is used to transmit the redundant optical signal and receive the redundant echo signal in the corresponding direction; The signal preprocessing module is used to preprocess and correct the local oscillator echo signal and the redundant echo signal to obtain a target beam signal; The wavefront correction module is used to calculate the real-time atmospheric turbulence value according to the target beam signal, and perform wavefront correction according to the real-time atmospheric turbulence value.

2. The wavefront correction system for a marine quantum key distribution system according to claim 1, characterized in that: The transmission optical path also includes: a light emission optical path and a light echo optical path; the light emission optical path is connected to the local oscillator optical antenna and the redundant optical antenna respectively, and the light echo optical path is connected to the local oscillator optical antenna and the redundant optical antenna respectively; The light emitting optical path is used to divide the initial optical signal into a local oscillator optical signal and a redundant optical signal, and transmit the local oscillator optical signal to the local oscillator optical antenna, and transmit the redundant optical signal to the redundant optical antenna; The light echo optical path is used to convert the local oscillator echo signal and the redundant echo signal into electrical signals, and transmit them to the signal preprocessing module.

3. The wavefront correction system for a marine quantum key distribution system according to claim 2, characterized in that: The light emitting optical path includes a plurality of isolators and a plurality of couplers; the isolators are connected in an alternating manner with the couplers; Wherein, the isolator is used to prevent the initial optical signal and the local oscillator optical signal from propagating in the reverse direction; The coupler is used to split the initial optical signal and the local oscillator optical signal, or to combine the initial optical signal and the local oscillator optical signal.

4. The wavefront correction system for a marine quantum key distribution system according to claim 2, characterized in that: The light echo optical path includes a circulator, an amplifier and a detector; the circulator, the amplifier and the detector are connected in sequence; Wherein, the circulator is used to transmit the local oscillator echo signal and the redundant echo signal according to a special optical path; The amplifier is used to amplify the local oscillator echo signal to enhance the power of the local oscillator echo signal; The detector is used for converting the local oscillator echo signal and the redundant echo signal into a local oscillator echo electrical signal and a redundant echo electrical signal.

5. The wavefront correction system for a marine quantum key distribution system according to claim 1, characterized in that: The wavefront correction module includes a field programmable logic gate array and a digital signal processor, and the field programmable logic gate array is connected to the digital signal processor; Wherein, the field programmable logic gate array is used to adjust the acquisition frequency and acquire the digital signal of the target beam signal; The digital signal processor is used to calculate the three-dimensional velocity vector components of the carrier to be measured according to the digital signal, and calculate the real-time atmospheric turbulence value according to the three-dimensional velocity vector components to perform wavefront correction.

6. The wavefront correction system for a marine quantum key distribution system according to claim 1, characterized in that: The laser is a narrow line width semiconductor laser with a wavelength of 1.55 μm and a power of 12 mW.

7. A wavefront correction method for a marine quantum key distribution system, based on the wavefront correction system for a marine quantum key distribution system as described in any one of claims 1 to 6, characterized in that: include: Establishing a horizontal space coordinate system based on the moving direction of the carrier to be measured, and establishing an antenna space coordinate system based on the target beam signal; When the horizontal space coordinate system coincides with the antenna space coordinate system, calculating the three-dimensional velocity vector component of the speed-measured carrier in the antenna space coordinate system according to the target beam signal and the antenna space coordinate system; When the horizontal space coordinate system does not coincide with the antenna space coordinate system, determining a coordinate conversion matrix according to a rotation angle between the antenna space coordinate system and the horizontal space coordinate system, and converting a three-dimensional velocity vector component on the antenna space coordinate system into a three-dimensional velocity vector component on the horizontal space coordinate system based on the coordinate conversion matrix; The real-time atmospheric turbulence value is calculated according to the three-dimensional velocity vector component on the horizontal space coordinate system to perform wavefront correction.

8. The wavefront correction method for a marine quantum key distribution system according to claim 7, characterized in that: When the horizontal space coordinate system coincides with the antenna space coordinate system, calculating the three-dimensional velocity vector component of the speed-measured carrier in the antenna space coordinate system according to the local oscillator echo signal and the antenna space coordinate system includes: Determine the beam unit vector in the antenna space coordinate system according to the target beam signal, and inversely calculate the carrier velocity vector of the carrier to be measured; Calculating a first angle between the target beam signal and each coordinate axis of the antenna space coordinate system according to the beam unit vector; The three-dimensional velocity vector component of the carrier to be measured in the antenna space coordinate system is calculated based on the beam unit vector, the carrier velocity vector and the first angle.

9. The wavefront correction method for a marine quantum key distribution system according to claim 8, characterized in that: The step of calculating the first angle between the target beam signal and each coordinate axis of the antenna space coordinate system according to the beam unit vector vector further includes: Calculating an angle between the beam unit vector and a first coordinate axis of the antenna space coordinate system according to the beam unit vector; Projecting the beam unit vector in a first preset plane, and calculating an angle between the projection and a second coordinate axis; The angles between the beam unit vector and the second and third coordinate axes of the antenna space coordinate system are calculated based on the trigonometric relationship, the angle between the beam unit vector and the first coordinate axis of the antenna space coordinate system, and the angle between the projection and the second coordinate axis.

10. The wavefront correction method for a marine quantum key distribution system according to claim 7, characterized in that: When the horizontal space coordinate system does not coincide with the antenna space coordinate system, determining a coordinate conversion matrix according to a rotation angle between the antenna space coordinate system and the horizontal space coordinate system, and converting a three-dimensional velocity vector component on the antenna space coordinate system into a three-dimensional velocity vector component on the horizontal space coordinate system based on the coordinate conversion matrix, comprises: Determine the pitch angle of the carrier to be measured in the horizontal space coordinate system and the roll angle of the carrier to be measured in the antenna space coordinate system based on the posture change of the carrier to be measured; Calculate a coordinate conversion matrix between the horizontal space coordinate system and the antenna space coordinate system according to the pitch angle and the roll angle; The three-dimensional velocity vector components in the antenna space coordinate system are converted into three-dimensional velocity vector components in the horizontal space coordinate system based on the coordinate conversion matrix.

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