OAM Inter-Satellite Optical Communication System Performance Evaluation Method, System, Device and Medium

Abstract

The present invention relates to the field of satellite communication technologies, and discloses a method, a system, a device and a medium for evaluating the performance of an OAM inter-satellite optical communication system. The method includes: establishing an OAM inter-satellite optical communication system model to obtain the field strength distribution of the light beam emitted from the source satellite to the destination satellite under the influence of pointing error; representing the field strength distribution of the light beam under the influence of pointing error in the form of a spiral harmonic function expansion, and performing a radial integration on the expansion coefficients in the form of the spiral harmonic function expansion to obtain the energy of each OAM mode in the light beam; according to the energy of each OAM mode in the light beam and the total energy of the entire light beam, obtaining the purity of each OAM mode, and combining the purities of multiple OAM modes to construct a probability density function and a cumulative distribution function of the OAM mode purity in the OAM inter-satellite optical communication system, so as to evaluate the performance of the OAM inter-satellite optical communication system.

Description

Technical Field

[0001] The present invention relates to the technical field of satellite communication, and particularly relates to a method, system, device and medium for evaluating the performance of an OAM inter-satellite optical communication system. Background Art

[0002] As an inherent property of light waves, Orbital Angular Momentum (OAM) has a higher multiplexing dimension to enable multiplexing, thereby greatly improving the capacity of optical communication systems. At the same time, the spatial orthogonality of OAM modes enhances the anti-interference ability of communication systems. Only by demodulating specific OAM modes can information be obtained, thus improving the security of communication. Therefore, conducting research on OAM inter-satellite optical communication is of great significance for satellite communication.

[0003] In an OAM inter-satellite optical communication system, pointing errors will be caused by both platform vibration and external perturbation factors, which have a significant impact on communication performance. Among them, platform vibration is one of the main reasons for pointing errors: during the orbital operation of a satellite, due to factors such as internal mechanical movement, temperature change, and external micro-impacts, different degrees of vibration will occur. These vibrations will directly affect the stability and accuracy of the optical communication system, resulting in deviation of the beam pointing. And external perturbation factors cannot be ignored either: the non-spherical gravitational field of the Earth will have a complex gravitational effect on the satellite, resulting in slight changes in the orbit; solar radiation pressure will also exert a continuous thrust on the satellite, further affecting the attitude and orbit of the satellite. These external perturbation factors will also cause pointing errors of the beam, thereby affecting communication performance.

[0004] Pointing errors will cause the beam to deviate from the predetermined path, thereby triggering crosstalk between OAM modes, reducing communication quality, and even causing communication interruption in severe cases. Therefore, evaluating the performance of an OAM inter-satellite optical communication system under the influence of pointing errors is crucial for supporting the development of future OAM inter-satellite optical communication technology. Summary of the Invention

[0005] The purpose of the present invention is to provide a method, system, device and medium for evaluating the performance of an OAM inter-satellite optical communication system, which can realize the performance evaluation of an OAM inter-satellite optical communication system under the influence of pointing errors.

[0006] To solve the above technical problems, an embodiment of the present invention provides a method for evaluating the performance of an OAM inter-satellite optical communication system, including the following steps:

[0007] Establish an OAM inter-satellite optical communication system model for OAM communication between the Earth, a source satellite and a destination satellite; wherein, there is a pointing error between the source satellite and the destination satellite due to platform vibration and external perturbation factors;

[0008] According to the OAM inter-satellite optical communication system model, obtain the field strength distribution of the light beam emitted from the source satellite to the destination satellite under the influence of pointing error;

[0009] Express the field strength distribution of the light beam under the influence of pointing error in the form of a helical harmonic function expansion, and perform a radial integration on the expansion coefficients in the form of the helical harmonic function expansion to obtain the energy of each OAM mode in the light beam;

[0010] According to the energy of each OAM mode in the light beam and the total energy of the entire light beam, obtain the purity of each OAM mode, and combine the purities of multiple OAM modes to construct the probability density function and cumulative distribution function of the OAM mode purity in the OAM inter-satellite optical communication system;

[0011] Evaluate the performance of the OAM inter-satellite optical communication system through the probability density function and cumulative distribution function of the OAM mode purity in the OAM inter-satellite optical communication system.

[0012] Optionally, the obtaining the field strength distribution of the light beam emitted from the source satellite to the destination satellite under the influence of pointing error according to the OAM inter-satellite optical communication system model includes:

[0013] Taking the source satellite as the origin, the direction of the angular momentum of the source satellite as the x-axis direction, the direction corresponding to the orbital radius of the source satellite as the z-axis, and determining the direction of the y-axis according to the directions of the x-axis and z-axis using the right-hand rule to establish a Hill coordinate system;

[0014] Obtain the first radial displacement of the light beam emitted from the source satellite to the destination satellite due to external perturbation factors r m1z ; where the first radial displacement occurs in the z-direction of the Hill coordinate system and follows a Gaussian distribution with an expectation of 0 and a variance of ;

[0015] Obtain the second radial displacement of the light beam emitted from the source satellite to the destination satellite due to platform vibration; where the second radial displacement is two independent radial displacements occurring in the z-direction and y-direction of the Hill coordinate system r m2z and r m2y , and both independent radial displacements follow a Gaussian distribution with an expectation of 0 and a variance of ;

[0016] Combine the first radial displacement of the light beam emitted from the source satellite to the destination satellite due to external perturbation and the second radial displacement due to platform vibration to obtain the target radial displacement between the source satellite and the destination satellite with pointing error , and the target radial displacement follows a Hoyt distribution;

[0017] Obtain the field strength distribution of the light beam emitted by the source satellite to the destination satellite under the influence of pointing error according to the target radial displacement between the source satellite and the destination satellite.

[0018] Optionally, the source satellite and the destination satellite use Laguerre-Gaussian (LG) beams for orbital angular momentum (OAM) communication. The optical field expression of the LG beam is:

[0019] ;

[0020] In the formula, l is the topological charge number of the vortex beam; is the Laguerre polynomial, p is the radial mode number of the LG beam; r is the radial distance from the spatial point to the transmission axis; is the azimuth angle; z is the transmission distance between the source satellite and the destination satellite; is the beam waist radius at the transmission distance z, w 0 is the initial beam waist radius; i is the imaginary unit; is the Rayleigh distance, and λ is the optical wavelength;

[0021] Let p = 0, and the optical field distribution of the LG beam is:

[0022] ;

[0023] According to the property that different modes of the LG beam are mutually orthogonal, it can be known that:

[0024] ;

[0025] In the formula, l 1 and l 2 are the topological charge numbers of the vortex beams of different modes respectively;

[0026] The field strength distribution of the light beam emitted by the source satellite under the influence of pointing error is:

[0027] ;

[0028] In the formula, is the optical axis offset angle.

[0029] Optionally, the field strength distribution of the light beam under the influence of pointing error is expressed in the form of a spiral harmonic function expansion, as shown in the following formula:

[0030] ;

[0031] In the formula, k is the number of OAM modes, is the expansion coefficient, which is expressed by the following formula:

[0032] ;

[0033] Performing a radial integration on the expansion coefficient in the form of the expansion of the helical harmonic function to obtain the energy of each OAM mode in the beam, as follows:

[0034] .

[0035] Optionally, the obtaining of the purity of each OAM mode includes:

[0036] Obtaining the weight value of the energy of each OAM mode in the beam accounting for the total energy of the entire beam according to the energy of each OAM mode in the beam and the total energy of the entire beam;

[0037] Obtaining the ratio of the total power of the beam received by the destination satellite to the total power of the beam transmitted by the source satellite according to the OAM inter-satellite optical communication system model;

[0038] Combining the weight value of the energy of each OAM mode in the beam accounting for the total energy of the entire beam and the ratio of the total power of the beam received by the destination satellite to the total power of the beam transmitted by the source satellite to obtain the purity of each OAM mode.

[0039] Optionally, the total energy of the entire beam is:

[0040] ;

[0041] The weight value of the energy of each OAM mode in the beam accounting for the total energy of the entire beam is:

[0042] ;

[0043] The total power of the beam received by the destination satellite and the total power of the beam transmitted by the source satellite The ratio is:

[0044] ;

[0045] In the formula, , is the radial displacement r m = 0 corresponds to the cylindrical coordinate system coordinates;

[0046] The purity of each OAM mode is:

[0047] ;

[0048] The probability density function of the OAM mode purity in the OAM inter-satellite optical communication system is represented in the form of a piecewise function:

[0049] ;

[0050] The cumulative distribution function of the OAM mode purity in the OAM inter-satellite optical communication system is:

[0051] ;

[0052] In the formula, h is the purity of each OAM mode, θ is the segmentation point, μ , a , b , c , k 1 , k 2 , k 3 , k 4 are the corresponding fitting parameters.

[0053] Optionally, the performance of the OAM inter-satellite optical communication system is evaluated through the probability density function and the cumulative distribution function of the OAM mode purity in the OAM inter-satellite optical communication system, including:

[0054] Through the probability density function and the cumulative distribution function of the OAM mode purity in the OAM inter-satellite optical communication system, obtain the outage probability and the ergodic capacity of the channel under the influence of pointing error of the OAM inter-satellite optical communication system, so as to evaluate the performance of the OAM inter-satellite optical communication system.

[0055] The embodiment of the present invention also provides an OAM inter-satellite optical communication system performance evaluation system, including:

[0056] A model establishment module, configured to establish an OAM inter-satellite optical communication system model for OAM communication between the earth, the source satellite, and the destination satellite; wherein, there is a pointing error between the source satellite and the destination satellite due to platform vibration and external perturbation factors;

[0057] A field strength acquisition module, configured to obtain the field strength distribution of the light beam emitted by the source satellite to the destination satellite under the influence of pointing error according to the OAM inter-satellite optical communication system model;

[0058] An energy acquisition module, configured to represent the field strength distribution of a light beam under the influence of pointing error in the form of a helical harmonic function expansion, and perform a radial integration on the expansion coefficients in the form of the helical harmonic function expansion to obtain the energy of each OAM mode in the light beam;

[0059] A function construction module, configured to obtain the purity of each OAM mode according to the energy of each OAM mode in the light beam and the total energy of the entire light beam, and construct a probability density function and a cumulative distribution function of the OAM mode purity in the OAM inter-satellite optical communication system by combining the purities of multiple OAM modes;

[0060] A performance evaluation module, configured to evaluate the performance of the OAM inter-satellite optical communication system through the probability density function and the cumulative distribution function of the OAM mode purity in the OAM inter-satellite optical communication system.

[0061] An embodiment of the present invention further provides a computer device, including: at least one processor; and a memory communicatively connected to the at least one processor; wherein, instructions executable by the at least one processor are stored in the memory, and when the instructions are executed by the at least one processor, the at least one processor is enabled to execute the above-mentioned OAM inter-satellite optical communication system performance evaluation method.

[0062] An embodiment of the present invention further provides a computer-readable storage medium, storing a computer program, and when the computer program is executed by a processor, the above-mentioned OAM inter-satellite optical communication system performance evaluation method is implemented.

[0063] The OAM inter-satellite optical communication system performance evaluation method provided by the present invention has at least the following beneficial effects:

[0064] A system model of the OAM inter-satellite optical communication system is established when there is a pointing error caused by platform vibration and external perturbation factors between the source satellite and the destination satellite, and the field strength distribution of the light beam emitted by the source satellite to the destination satellite under the influence of the pointing error is obtained. The field strength distribution of the light beam under the influence of the pointing error is represented in the form of a helical harmonic function expansion, and a radial integration is performed on the expansion coefficients in the form of the helical harmonic function expansion, so that the energy of each OAM mode in the light beam can be obtained. Then, according to the energy of each OAM mode in the light beam and the total energy of the entire light beam, the purity of each OAM mode can be obtained. Finally, the performance of the OAM inter-satellite optical communication system is evaluated based on the probability density function and the cumulative distribution function constructed from the purities of multiple OAM modes.

[0065] This solution takes into account the energy of each OAM mode in the beam emitted by the source satellite under the influence of pointing error factors, and based on this, judges the impact of crosstalk between multiple OAM modes caused by pointing error on the performance of the OAM inter-satellite optical communication system, realizing the performance evaluation of the OAM inter-satellite optical communication system under the influence of pointing error. Description of the Drawings

[0066] One or more embodiments are exemplarily illustrated by the pictures in the corresponding drawings, and these exemplary illustrations do not constitute a limitation on the embodiments.

[0067] Figure 1 is a flowchart of a method for evaluating the performance of an OAM inter-satellite optical communication system provided according to an embodiment of the present invention;

[0068] Figure 2 is a system diagram including the Earth and communication satellites provided according to an embodiment of the present invention;

[0069] Figure 3 is a comparison of the fitting PDF and statistical PDF of the purity of the OAM inter-satellite optical communication mode provided according to an embodiment of the present invention Figure 1 ;

[0070] Figure 4 is a comparison of the fitting PDF and statistical PDF of the purity of the OAM inter-satellite optical communication mode provided according to an embodiment of the present invention Figure 2 ;

[0071] Figure 5 is a comparison of the fitting PDF and statistical PDF of the purity of the OAM inter-satellite optical communication mode provided according to an embodiment of the present invention Figure 3 ;

[0072] Figure 6 is a comparison of the fitting PDF and statistical PDF of the purity of the OAM inter-satellite optical communication mode provided according to an embodiment of the present invention Figure 4 。 Detailed Embodiments

[0073] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the embodiments of the present invention will be described in detail below with reference to the accompanying drawings. However, those of ordinary skill in the art can understand that in the embodiments of the present invention, many technical details are provided to help readers better understand the present invention. However, even without these technical details and various changes and modifications based on the following embodiments, the technical solutions required to be protected by the present invention can still be implemented. The following division of each embodiment is for convenience of description and should not constitute any limitation on the specific implementation manner of the present invention. Each embodiment can be combined and cross-referenced with each other on the premise of not conflicting.

[0074] One embodiment of the present invention relates to a method for evaluating the performance of an OAM inter-satellite optical communication system. The implementation details of the method for evaluating the performance of the OAM inter-satellite optical communication system in this embodiment will be specifically described below. The following content is only the implementation details provided for convenient understanding and is not necessary for implementing this solution.

[0075] The specific process of the method for evaluating the performance of the OAM inter-satellite optical communication system in this embodiment can be as Figure 1 shown, including:

[0076] Step 101, establish an OAM inter-satellite optical communication system model for OAM communication between the earth, the source satellite, and the destination satellite; wherein, there is a pointing error between the source satellite and the destination satellite due to platform vibration and external perturbation factors.

[0077] Step 102, according to the OAM inter-satellite optical communication system model, obtain the field strength distribution of the light beam emitted by the source satellite to the destination satellite under the influence of the pointing error.

[0078] Specifically, the OAM inter-satellite optical communication system model established in this embodiment is implemented based on the system as Figure 2 shown. First, taking the source satellite as the origin, the direction of the angular momentum of the source satellite as the x-axis direction, the direction corresponding to the orbital radius of the source satellite as the z-axis, and according to the directions of the x-axis and z-axis, the direction of the y-axis is determined by the right-hand rule to establish a Hill coordinate system. The radial displacement r m1z of the light beam emitted by the source satellite to the destination satellite caused by external perturbation factors only occurs in the satellite orbital plane (z direction), and the satellite platform vibration will also cause radial displacement. Considering the radial displacement caused by the platform's own vibration as two independently distributed radial displacements in the vertical direction (z direction) and the horizontal direction (y direction). Therefore, in this embodiment, the first radial displacement r m1z of the light beam emitted by the source satellite to the destination satellite caused by external perturbation factors and the second radial displacement caused by platform vibration are obtained. Among them, the first radial displacement occurs in the z direction of the Hill coordinate system and follows a Gaussian distribution with an expectation of 0 and a variance of , that is ; the second radial displacement is two independent radial displacements r m2z and r m2y occurring in the z direction and the y direction of the Hill coordinate system, and both independent radial displacements follow a Gaussian distribution with an expectation of 0 and a variance of , that is , .

[0079] At this time, according to the target radial displacement between the source satellite and the destination satellite, the field strength distribution of the light beam emitted by the source satellite towards the destination satellite under the influence of pointing error is obtained.

[0080] It is assumed that the source satellite and the destination satellite use Laguerre-Gaussian (LG) beams for orbital angular momentum (OAM) communication. The LG beam is a commonly used beam in OAM communication, and the optical field expression of the LG beam is:

[0081] ;

[0082] In the formula, l is the topological charge number of the vortex beam; is the Laguerre polynomial, p is the radial mode number of the LG beam; r is the radial distance from the spatial point to the transmission axis; is the azimuth angle; z is the transmission distance between the source satellite and the destination satellite; is the beam waist radius of the light beam at the transmission distance z, w 0 is the initial beam waist radius; i is the imaginary unit; is the Rayleigh distance, and λ is the optical wavelength.

[0083] For a fixed p , the LG beam always has orthogonality. For the convenience of research, let p = 0, and the optical field distribution of the LG beam is:

[0084] ;

[0085] At the same time, according to the property that different modes of the LG beam are mutually orthogonal, it can be known that:

[0086] ;

[0087] In the formula, l 1 and l 2 are the topological charge numbers of the vortex beams of different modes respectively.

[0088] Then, the field strength distribution of the light beam emitted by the source satellite under the influence of pointing error is:

[0089] ;

[0090] In the formula, is the optical axis offset angle.

[0091] From As can be seen from this term, the radial displacement will cause a change in the phase of the OAM wave. By performing a Bessel series expansion on this term, the field strength distribution formula of the beam emitted by the source satellite under the influence of the pointing error can be further transformed into:

[0092] ;

[0093] In the formula, I m is m the modified Bessel function of the first kind of order J n is n the formula of the Bessel function of the first kind of order . From this formula, it can be found that the phase change caused by the radial displacement will further lead to crosstalk between OAM modes.

[0094] Step 103: Express the field strength distribution of the beam under the influence of the pointing error in the form of a helical harmonic function expansion, and perform a radial integration on the expansion coefficients in the form of the helical harmonic function expansion to obtain the energy of each OAM mode in the beam.

[0095] Specifically, for the convenience of subsequent derivation, in this embodiment, the field strength distribution of the beam under the influence of the pointing error is expressed in the form of a helical harmonic function expansion, as shown in the following formula:

[0096] ;

[0097] In the formula, k is the number of OAM modes, is the expansion coefficient, which is expressed by the following formula:

[0098] ;

[0099] Performing a radial integration on the expansion coefficients in the form of the helical harmonic function expansion to obtain the energy of each OAM mode in the beam is as follows:

[0100] .

[0101] Step 104: According to the energy of each OAM mode in the beam and the total energy of the entire beam, obtain the purity of each OAM mode, and combine the purities of multiple OAM modes to construct the probability density function and cumulative distribution function of the OAM mode purity in the OAM satellite-to-satellite optical communication system.

[0102] In an example, in this embodiment, according to the energy of each OAM mode in the beam and the total energy of the entire beam, the weight value of the energy of each OAM mode in the entire beam is obtained, and it is used as the purity of each OAM mode.

[0103] Among them, since the total energy of the entire light beam can be expressed as:

[0104] ;

[0105] then the weight value of the energy of each OAM mode in the light beam accounting for the total energy of the entire light beam can be calculated:

[0106] .

[0107] In another example, after obtaining the weight value of the energy of each OAM mode in the light beam accounting for the total energy of the entire light beam according to the energy of each OAM mode in the light beam and the total energy of the entire light beam in this embodiment, according to the OAM inter-satellite optical communication system model, the ratio of the total power of the light beam emitted by the source satellite to the total power of the light beam received by the destination satellite is obtained. Then, combining the weight value of the energy of each OAM mode in the light beam accounting for the total energy of the entire light beam and the ratio of the total power of the light beam emitted by the source satellite to the total power of the light beam received by the destination satellite, the purity of each OAM mode is obtained.

[0108] Specifically, since the light intensity distributions of different modes are different, under different transmitted OAM modes and pointing errors, the power received by the receiver is also different. In the case of a large transmitted mode and a large pointing error, the receiving end cannot receive all the transmitted power, so the power attenuation caused by the pointing error should also be considered. The power attenuation caused by the pointing error can be represented by the ratio of the total received power Pr and the total transmitted power Pt (that is, the ratio of the total power of the light beam emitted by the source satellite to the total power of the light beam received by the destination satellite):

[0109] ;

[0110] In the formula, , is the cylindrical coordinate corresponding to the radial displacement r m =0.

[0111] Then the purity h of each OAM mode affected by the final pointing error is expressed as:

[0112] .

[0113] Next, combining the purity of multiple OAM modes, the probability density function (PDF) and cumulative distribution function (CDF) of the OAM mode purity in the OAM inter-satellite optical communication system are constructed. Theoretically, the target radial displacement caused by the pointing error r m The corresponding PDF of the OAM mode purity can be obtained from the distribution, but in actual calculations, it involves the Hoyt distribution and the related integral operations of the Bessel series, and it is difficult to directly calculate the relevant closed-form expressions. Therefore, this embodiment adopts a fitting scheme to describe the PDF of the OAM mode purity. Here, a piecewise function form is used to describe the PDF of the OAM mode purity under the influence of the pointing error. At this time, the PDF expression of the OAM purity can be expressed in the following form:

[0114] ;

[0115] Furthermore, the cumulative distribution function of the OAM mode purity in the corresponding OAM inter-satellite optical communication system can be derived:

[0116] ;

[0117] In the formula, h is the purity of each OAM mode, θ is the segmentation point, μ , a , b , c , k 1 , k 2 , k 3 , k 4 are the corresponding fitting parameters.

[0118] In one example, this embodiment can verify the rationality of the proposed distribution. The point estimation method has the advantages of providing specific estimated values of the overall parameters, being more intuitive and concise in expression, and being able to provide estimation errors, etc. Therefore, the equal-probability point estimation method is selected to solve the fitting parameters of the OAM mode purity. The fitting steps of the point estimation method are as follows:

[0119] 1. Arrange the random data in ascending order X 1 , X N , and take k points at equal intervals from it.

[0120] 2. The selected sample points can be expressed as , i = 1… k .

[0121] 3. The probability corresponding to the selected sample points can be expressed as p i =N i / N . N i Corresponding to the number of data less than X i .

[0122] 4. According to the formula F ( X i ) = pi . Use the least squares method to find the relevant parameters. The more points are taken, the more accurate the parameters obtained.

[0123] For the proposed PDF formula in the form of a piecewise function, traverse the value of the breakpoint θ from 0 to 1. After each value is taken, use the point estimation method to solve the relevant parameters on both sides of the breakpoint respectively, and record the root mean square error (MSE) between the empirical PDF. The final breakpoint with the smallest MSE is the optimal breakpoint, and the corresponding parameters are the optimal parameters.

[0124] For example, referring to Figures 3 to 6 It can be seen that using the parameters derived above, the purity PDF of the OAM inter-satellite optical communication mode is fitted under different OAM modes and pointing error conditions, and the root mean square error between the statistical PDF results is all within 3×10 -6 Below, indicating that the proposed fitted PDF formula can well characterize the purity distribution of the OAM mode under the influence of pointing error. The CDF formula can also be verified with reference to the above scheme, which will not be elaborated here.

[0125] Step 105, evaluate the performance of the OAM inter-satellite optical communication system through the probability density function and cumulative distribution function of the OAM mode purity in the OAM inter-satellite optical communication system.

[0126] Specifically, through the probability density function and cumulative distribution function of the OAM mode purity in the OAM inter-satellite optical communication system, obtain the channel performance such as the outage probability and ergodic capacity of the channel under the influence of pointing error in the OAM inter-satellite optical communication system, so as to evaluate the performance of the OAM inter-satellite optical communication system.

[0127] It can be understood that in this embodiment, the performance of the OAM inter-satellite optical communication system is judged under the influence of the pointing error factor. In fact, the performance of the OAM inter-satellite optical communication system under other different influencing factors can also be evaluated.

[0128] In this embodiment, a system model is established for the OAM inter-satellite optical communication system when there is a pointing error between the source satellite and the destination satellite due to platform vibration and external perturbation factors. The field strength distribution of the light beam emitted by the source satellite to the destination satellite under the influence of the pointing error is obtained. The field strength distribution of the light beam under the influence of the pointing error is expressed in the form of a spiral harmonic function expansion. By performing a radial integration on the expansion coefficients in the form of the spiral harmonic function expansion, the energy of each OAM mode in the light beam can be obtained. Then, based on the energy of each OAM mode in the light beam and the total energy of the entire light beam, the purity of each OAM mode can be obtained. Finally, based on the probability density function and cumulative distribution function constructed from the purities of multiple OAM modes, the performance of the OAM inter-satellite optical communication system is evaluated. This solution takes into account the energy occupied by each OAM mode in the light beam emitted by the source satellite under the influence of the pointing error factor, and based on this, judges the impact of the crosstalk between multiple OAM modes caused by the pointing error on the performance of the OAM inter-satellite optical communication system, realizing the performance evaluation of the OAM inter-satellite optical communication system under the influence of the pointing error.

[0129] This embodiment is applicable to the OAM inter-satellite optical communication scenario, especially for the analysis of the performance of the OAM inter-satellite optical communication system under the influence of the pointing error, and has important application value. For example, in the fields of deep space communication and satellite constellation networking, the method of the present invention can be effectively applied. In addition, by combining with the existing technology, the present invention is expected to achieve greater breakthroughs in the field of OAM inter-satellite optical communication, promoting the development of OAM satellite optical communication networking and deep space OAM optical communication. This not only provides new opportunities for the innovation of OAM inter-satellite optical communication technology, but also brings more advanced and reliable solutions for deep space OAM optical communication.

[0130] The step division of the above various methods is only for clear description. When implemented, they can be combined into one step or some steps can be split into multiple steps. As long as they include the same logical relationship, they are all within the protection scope of the present invention; adding insignificant modifications or introducing insignificant designs to the algorithm or process, but not changing the core design of its algorithm and process are all within the protection scope of the invention.

[0131] Another embodiment of the present invention relates to a performance evaluation system for an OAM inter-satellite optical communication system. The implementation details of the performance evaluation system for the OAM inter-satellite optical communication system in this embodiment are specifically described below. The following content is only implementation details provided for convenient understanding and is not necessary for implementing this solution. The performance evaluation system for the OAM inter-satellite optical communication system in this embodiment includes:

[0132] A model establishment module, configured to establish an OAM inter-satellite optical communication system model for OAM communication between the Earth, a source satellite, and a destination satellite; wherein, there is a pointing error between the source satellite and the destination satellite due to platform vibration and external perturbation factors.

[0133] An electric field strength acquisition module, configured to acquire the electric field strength distribution of the light beam emitted by the source satellite to the destination satellite under the influence of the pointing error according to the OAM inter-satellite optical communication system model.

[0134] An energy acquisition module, configured to represent the electric field strength distribution of the light beam under the influence of the pointing error in the form of a spiral harmonic function expansion, and perform a radial integral on the expansion coefficients in the form of the spiral harmonic function expansion to obtain the energy of each OAM mode in the light beam.

[0135] A function construction module, configured to obtain the purity of each OAM mode according to the energy of each OAM mode in the light beam and the total energy of the entire light beam, and construct a probability density function and a cumulative distribution function of the OAM mode purity in the OAM inter-satellite optical communication system by combining the purities of multiple OAM modes.

[0136] A performance evaluation module, configured to evaluate the performance of the OAM inter-satellite optical communication system through the probability density function and the cumulative distribution function of the OAM mode purity in the OAM inter-satellite optical communication system.

[0137] It is not difficult to find that this embodiment is a system embodiment corresponding to the above method embodiment, and this embodiment can be implemented in cooperation with the above method embodiment. The relevant technical details and technical effects mentioned in the above embodiment are still valid in this embodiment. To avoid repetition, they are not elaborated here. Correspondingly, the relevant technical details mentioned in this embodiment can also be applied in the above embodiment.

[0138] It is worth mentioning that each module involved in this embodiment is a logical module. In practical applications, a logical unit can be a physical unit, a part of a physical unit, or can be implemented by a combination of multiple physical units. In addition, to highlight the innovative part of the present invention, units that are not closely related to solving the technical problems proposed by the present invention are not introduced in this embodiment, but this does not mean that there are no other units in this embodiment.

[0139] Another embodiment of the present invention relates to a computer device, including: at least one processor; and a memory communicatively connected to the at least one processor; wherein, the memory stores instructions executable by the at least one processor, and the instructions are executed by the at least one processor to enable the at least one processor to execute the OAM inter-satellite optical communication system performance evaluation method in the above embodiments.

[0140] Among them, the memory and the processor are connected in a bus manner. The bus may include any number of interconnected buses and bridges, and the bus connects various circuits of one or more processors and the memory together. The bus can also connect various other circuits such as peripheral devices, voltage regulators, and power management circuits, which are well known in the art, so they will not be further described herein. The bus interface provides an interface between the bus and the transceiver. The transceiver can be a single component or multiple components, such as multiple receivers and transmitters, and provides a unit for communicating with various other devices over a transmission medium. The data processed by the processor is transmitted over a wireless medium via an antenna. Further, the antenna also receives data and transmits the data to the processor.

[0141] The processor is responsible for managing the bus and general processing, and can also provide various functions, including timing, peripheral interface, voltage regulation, power management, and other control functions. The memory can be used to store the data used by the processor when executing operations.

[0142] Another embodiment of the present invention relates to a computer-readable storage medium storing a computer program. When the computer program is executed by a processor, the method embodiments described above are implemented.

[0143] That is, those skilled in the art can understand that all or part of the steps of implementing the methods in the above embodiments can be completed by instructing relevant hardware through a program. The program is stored in a storage medium and includes several instructions to enable a device (which can be a single-chip microcomputer, a chip, etc.) or a processor to execute all or part of the steps of the methods described in various embodiments of the present invention. The foregoing storage medium includes: various media such as USB flash drives, mobile hard disks, read-only memories (ROM), random access memories (RAM), magnetic disks, or optical discs that can store program codes.

[0144] Those of ordinary skill in the art can understand that the above embodiments are specific embodiments for implementing the present invention, and in practical applications, various changes can be made in form and details without departing from the spirit and scope of the present invention.

Claims

1. A method for evaluating the performance of an OAM intersatellite optical communication system, characterized in that: include: Establish an OAM intersatellite optical communication system model for OAM communication between the Earth, the source satellite and the destination satellite; there is a pointing error between the source satellite and the destination satellite caused by platform vibration and external perturbation factors; According to the OAM intersatellite optical communication system model, the field intensity distribution of the light beam emitted by the source satellite to the destination satellite under the influence of pointing error is obtained; The field intensity distribution of the light beam under the influence of pointing error is expressed as the form of spiral harmonic function expansion, and the expansion coefficient in the form of spiral harmonic function expansion is radially integrated to obtain the energy of each OAM mode in the light beam; According to the energy of each OAM mode in the light beam and the total energy of the entire light beam, the purity of each OAM mode is obtained, and the probability density function and cumulative distribution function of the purity of the OAM mode in the OAM intersatellite optical communication system are constructed by combining the purity of multiple OAM modes. The performance of OAM intersatellite optical communication system is evaluated through the probability density function and cumulative distribution function of OAM mode purity in OAM intersatellite optical communication system; Wherein, obtaining the field intensity distribution of the light beam emitted by the source satellite to the destination satellite under the influence of the pointing error according to the OAM intersatellite optical communication system model includes: The Hill coordinate system is established by taking the source satellite as the origin, the direction of the angular momentum of the source satellite as the x-axis direction, the direction corresponding to the orbit radius of the source satellite as the z-axis, and using the right-hand rule to determine the direction of the y-axis based on the directions of the x-axis and the z-axis; Obtain the first radial displacement r of the light beam emitted by the source satellite to the destination satellite due to external perturbations m1z ; The first radial displacement occurs in the z direction of the Hill coordinate system and has an expectation of 0 and a variance of Gaussian distribution of Obtain the second radial displacement of the light beam emitted by the source satellite to the destination satellite due to the platform vibration; wherein the second radial displacement is two independent radial displacements r occurring in the z direction and y direction of the Hill coordinate system m2z and r m2y , and the two independent radial displacements are both expected to be 0, and the variance is Gaussian distribution of Combined with the first radial displacement of the light beam emitted by the source satellite to the destination satellite due to external perturbation and the second radial displacement caused by platform vibration, the target radial displacement between the source satellite and the destination satellite with pointing error is obtained. The target radial displacement follows the Hoyt distribution; According to the target radial displacement between the source satellite and the destination satellite, the field intensity distribution of the light beam emitted by the source satellite to the destination satellite under the influence of the pointing error is obtained.

2. The OAM intersatellite optical communication system performance evaluation method according to claim 1, characterized in that: The source satellite and the destination satellite use Laguerre-Gaussian LG beams for OAM communication, and the light field expression of the LG beam is: Where l is the topological charge of the vortex beam; is the Laguerre polynomial, p is the radial mode number of the LG beam; r is the radial distance from the space point to the transmission axis; φ is the azimuth; z is the transmission distance between the source satellite and the destination satellite; is the beam waist radius at the transmission distance z, w0 is the initial beam waist radius; i is the imaginary unit; is the Rayleigh distance, λ is the wavelength of light; Let p = 0, the light field distribution of the LG beam is: According to the property that different modes of LG beams are orthogonal to each other, we know that: Where l1 and l2 are the topological charges of vortex beams of different modes respectively; The field intensity distribution of the light beam emitted by the source satellite under the influence of pointing error is: In the formula, σ φ is the optical axis offset angle.

3. The OAM intersatellite optical communication system performance evaluation method according to claim 2, characterized in that: The field intensity distribution of the light beam under the influence of the pointing error is expressed as the form of the spiral harmonic function expansion, as shown in the following formula: Where k is the number of OAM modes, a k (r,z) is the expansion coefficient, which is expressed by the following formula: The expansion coefficients in the form of the spiral harmonic function expansion are radially integrated to obtain the energy of each OAM mode in the beam, as shown below:

4. The OAM intersatellite optical communication system performance evaluation method according to claim 3, characterized in that: The obtaining of the purity of each OAM mode comprises: According to the energy of each OAM mode in the light beam and the total energy of the entire light beam, a weight value of the energy of each OAM mode in the light beam to the total energy of the entire light beam is obtained; According to the OAM intersatellite optical communication system model, the ratio of the total power of the light beam received by the destination satellite to the total power of the light beam transmitted by the source satellite is obtained; The purity of each OAM mode is obtained by combining the weight value of the energy of each OAM mode in the light beam to the total energy of the entire light beam, and the ratio of the total power of the light beam received by the destination satellite to the total power of the light beam emitted by the source satellite.

5. The OAM intersatellite optical communication system performance evaluation method according to claim 4, characterized in that: The total energy of the entire beam is: The weight of the energy of each OAM mode in the beam to the total energy of the entire beam is: The total power P of the beam received by the destination satellite r The total power P of the beam emitted by the source satellite t The ratio is: Where r0, φ0 is the radial displacement r m =0 when the corresponding cylindrical coordinate system coordinates; The purity of each OAM mode is: h=h kl h a ; The probability density function of the purity of the OAM mode in the OAM intersatellite optical communication system is expressed in the form of a piecewise function: The cumulative distribution function of the OAM mode purity in the OAM intersatellite optical communication system is: Where h is the purity of each OAM mode, θ is the segmentation point, and μ, a, b, c, k1, k2, k3, and k4 are the corresponding fitting parameters.

6. The OAM intersatellite optical communication system performance evaluation method according to claim 1, characterized in that: The performance of the OAM inter-satellite optical communication system is evaluated by using the probability density function and cumulative distribution function of the purity of the OAM mode in the OAM inter-satellite optical communication system, including: Through the probability density function and cumulative distribution function of the OAM mode purity in the OAM inter-satellite optical communication system, the interruption probability and ergodic capacity of the channel under the influence of pointing error of the OAM inter-satellite optical communication system are obtained to evaluate the performance of the OAM inter-satellite optical communication system.

7. An OAM intersatellite optical communication system performance evaluation system, characterized in that: include: A model building module is used to build an OAM intersatellite optical communication system model when OAM communication is carried out between the earth, the source satellite and the destination satellite; wherein there is a pointing error between the source satellite and the destination satellite caused by platform vibration and external perturbation factors; A field intensity acquisition module is used to obtain the field intensity distribution of the light beam emitted by the source satellite to the destination satellite under the influence of the pointing error according to the OAM intersatellite optical communication system model; An energy acquisition module is used to express the field intensity distribution of the light beam under the influence of the pointing error as a spiral harmonic function expansion form, and radially integrate the expansion coefficients in the spiral harmonic function expansion form to obtain the energy of each OAM mode in the light beam; A function construction module is used to obtain the purity of each OAM mode according to the energy of each OAM mode in the light beam and the total energy of the entire light beam, and to construct the probability density function and cumulative distribution function of the purity of the OAM mode in the OAM intersatellite optical communication system by combining the purity of multiple OAM modes; A performance evaluation module, used for evaluating the performance of the OAM inter-satellite optical communication system through the probability density function and cumulative distribution function of the purity of the OAM mode in the OAM inter-satellite optical communication system; The field strength acquisition module is further used to establish a Hill coordinate system by taking the source satellite as the origin, the direction of the angular momentum of the source satellite as the x-axis direction, and the direction corresponding to the orbit radius of the source satellite as the z-axis, and determining the direction of the y-axis using the right-hand rule according to the directions of the x-axis and the z-axis; Obtain the first radial displacement r of the light beam emitted by the source satellite to the destination satellite due to external perturbations m1z ; The first radial displacement occurs in the z direction of the Hill coordinate system and has an expectation of 0 and a variance of Gaussian distribution of Obtain the second radial displacement of the light beam emitted by the source satellite to the destination satellite due to the platform vibration; wherein the second radial displacement is two independent radial displacements r occurring in the z direction and y direction of the Hill coordinate system m2z and r m2y , and the two independent radial displacements are both expected to be 0, and the variance is Gaussian distribution of Combined with the first radial displacement of the light beam emitted by the source satellite to the destination satellite due to external perturbation and the second radial displacement caused by platform vibration, the target radial displacement between the source satellite and the destination satellite with pointing error is obtained. The target radial displacement follows the Hoyt distribution; According to the target radial displacement between the source satellite and the destination satellite, the field intensity distribution of the light beam emitted by the source satellite to the destination satellite under the influence of the pointing error is obtained.

8. A computer device, characterized in that: include: at least one processor; And, a memory communicatively connected to the at least one processor; wherein the memory stores instructions executable by the at least one processor, and the instructions are executed by the at least one processor so that the at least one processor can execute the OAM inter-satellite optical communication system performance evaluation method as described in any one of claims 1 to 6.

9. A computer-readable storage medium storing a computer program, characterized in that: When the computer program is executed by a processor, the OAM inter-satellite optical communication system performance evaluation method according to any one of claims 1 to 6 is implemented.

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