Performance evaluation method, system and equipment for OAM inter-satellite optical communication system and medium

Abstract

The invention relates to the technical field of satellite communication, and discloses an OAM inter-satellite optical communication system performance evaluation method, system and device and a medium. The method comprises the following steps: establishing an OAM inter-satellite optical communication system model to obtain field intensity distribution of a light beam emitted from an information source satellite to an information sink satellite under the influence of a pointing error; expressing the field intensity distribution of the light beam under the influence of the pointing error as a spiral harmonic function expansion form, and carrying out radial integration on an expansion coefficient in the spiral harmonic function expansion form to obtain the energy of each OAM mode in the light beam; obtaining the purity of each OAM mode according to the energy of each OAM mode in the light beam and the total energy of the whole light beam, and constructing a probability density function and a cumulative distribution function of the OAM mode purity in the OAM inter-satellite optical communication system in combination with the purity of multiple OAM modes, so as to evaluate the performance of the OAM inter-satellite optical communication system.

Description

Technical Field

[0001] The present invention relates to the field of satellite communication technology, and in particular to an OAM inter-satellite optical communication system performance evaluation method, system, equipment and medium. Background Art

[0002] Orbital Angular Momentum (OAM), as an inherent property of light waves, has a higher multiplexing dimension and can achieve 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, thereby improving the security of communication. Therefore, conducting research on OAM intersatellite optical communications is of great significance to satellite communications.

[0003] In OAM intersatellite optical communication systems, platform vibration and external perturbations can cause pointing errors, which have a significant impact on communication performance. Among them, platform vibration is one of the main causes of pointing errors: during orbital motion, satellites will experience varying degrees of vibration due to internal mechanical movement, temperature changes, and external minor impacts. These vibrations will directly affect the stability and accuracy of the optical communication system, causing deviations in the pointing direction of the light beam. External perturbations cannot be ignored either: the earth's non-spherical gravity field will produce complex gravitational effects on satellites, resulting in slight changes in orbit; solar light pressure will also produce continuous thrust on satellites, further affecting the satellite's attitude and orbit. These external perturbations will also cause pointing errors in the light beam, which will in turn affect communication performance.

[0004] Pointing errors can cause the light beam to deviate from the intended path, which in turn causes crosstalk between OAM modes, degrading communication quality, and even leading to communication interruption in severe cases. Therefore, evaluating the performance of OAM intersatellite optical communication systems under the influence of pointing errors is crucial to supporting the development of future OAM intersatellite optical communication technologies. Summary of the invention

[0005] The object 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 the OAM inter-satellite optical communication system under the influence of pointing errors.

[0006] In order 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, comprising the following steps: 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 the OAM inter-satellite optical communication system is evaluated through the probability density function and cumulative distribution function of the OAM mode purity in the OAM inter-satellite optical communication system.

[0007] Optionally, obtaining, according to the OAM intersatellite optical communication system model, a field intensity distribution of a light beam emitted by a source satellite to a destination satellite under the influence of a pointing error 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 of the light beam emitted by the source satellite to the destination satellite due to external perturbations r 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 occurring in the z direction and y direction of the Hill coordinate system r 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 obeys 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.

[0008] Optionally, 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: ; In the formula, 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 spatial point to the transmission axis; 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, w 0 is the initial beam waist radius; i is an imaginary unit; is the Rayleigh distance, λ is the wavelength of light; make 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: ; In the formula, l 1 and l 2 are the topological charges of vortex beams of different modes; The field intensity distribution of the light beam emitted by the source satellite under the influence of pointing error is: ; In the formula, is the optical axis offset angle.

[0009] Optionally, the field intensity distribution of the light beam under the influence of the pointing error is expressed as a spiral harmonic function expansion form, as shown in the following formula: ; In the formula, k is the number of OAM modes, is the expansion coefficient, 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: .

[0010] Optionally, obtaining the purity of each OAM mode includes: 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.

[0011] Optionally, the total energy of the entire light 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 of the beam received by the destination satellite The total power of the beam emitted by the source satellite The ratio is: ; In the formula, , is the radial displacement r m =0 corresponding cylindrical coordinates; The purity of each OAM mode is: ; 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: ; 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.

[0012] Optionally, the evaluating the performance of the OAM inter-satellite optical communication system by using the probability density function and the cumulative distribution function of the purity of the OAM mode in the OAM inter-satellite optical communication system includes: 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.

[0013] An embodiment of the present invention further provides an OAM inter-satellite optical communication system performance evaluation system, comprising: 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; The performance evaluation module is used to evaluate 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.

[0014] An embodiment of the present invention also provides a computer device, comprising: 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 above-mentioned OAM inter-satellite optical communication system performance evaluation method.

[0015] An embodiment of the present invention further provides a computer-readable storage medium storing a computer program, wherein the computer program implements the above-mentioned OAM inter-satellite optical communication system performance evaluation method when executed by a processor.

[0016] The OAM intersatellite optical communication system performance evaluation method provided by the present invention has at least the following beneficial effects: A system model of the OAM intersatellite optical communication system is established when there is a pointing error between the source satellite and the destination satellite due to platform vibration and external perturbation factors, and 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. The field intensity distribution of the light beam under the influence of the pointing error is expressed as a spiral harmonic function expansion form, and the expansion coefficients in the spiral harmonic function expansion form are 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 can be obtained. Finally, the probability density function and cumulative distribution function constructed based on the purity of multiple OAM modes are used to evaluate the performance of the OAM intersatellite optical communication system.

[0017] This scheme takes into account the energy occupied by each OAM mode in the light 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, thereby realizing the performance evaluation of the OAM inter-satellite optical communication system under the influence of pointing error. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] One or more embodiments are exemplarily described by the pictures in the corresponding drawings, and these exemplary descriptions do not constitute limitations on the embodiments.

[0019] Figure 1 is a flow chart of a method for evaluating performance of an OAM inter-satellite optical communication system provided according to an embodiment of the present invention; Figure 2 is a diagram of a system including the earth and a communication satellite provided according to an embodiment of the present invention; Figure 3 A comparison between the purity fitting PDF and the statistical PDF of an OAM intersatellite optical communication mode provided according to an embodiment of the present invention Figure 1 ; Figure 4 A comparison between the purity fitting PDF and the statistical PDF of an OAM intersatellite optical communication mode provided according to an embodiment of the present invention Figure 2 ; Figure 5 A comparison between the purity fitting PDF and the statistical PDF of an OAM intersatellite optical communication mode provided according to an embodiment of the present invention Figure 3 ; Figure 6 A comparison between the purity fitting PDF and the statistical PDF of an OAM intersatellite optical communication mode provided according to an embodiment of the present invention Figure 4 . DETAILED DESCRIPTION

[0020] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings. However, it will be appreciated by those skilled in the art that in the embodiments of the present invention, many technical details are proposed in order to enable the reader to better understand the present invention. However, even without these technical details and various changes and modifications based on the following embodiments, the technical scheme claimed in the present invention can be implemented. The division of the following embodiments is for the convenience of description and should not constitute any limitation on the specific implementation of the present invention. The various embodiments can be combined and referenced with each other without contradiction.

[0021] An embodiment of the present invention relates to an OAM inter-satellite optical communication system performance evaluation method. The implementation details of the OAM inter-satellite optical communication system performance evaluation method of this embodiment are specifically described below. The following content is only the implementation details provided for easy understanding and is not necessary for implementing this solution.

[0022] The specific process of the OAM inter-satellite optical communication system performance evaluation method of this embodiment can be as follows: Figure 1 As shown, including: Step 101, establishing an OAM inter-satellite optical communication system model when OAM communication is performed between the earth, a source satellite, and a destination satellite; wherein there is a pointing error between the source satellite and the destination satellite caused by platform vibration and external perturbation factors.

[0023] Step 102: According to the OAM inter-satellite 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 the pointing error is obtained.

[0024] Specifically, the OAM intersatellite optical communication system model established in this embodiment is based on the following Figure 2 First, the source satellite is taken as the origin, the direction of the source satellite angular momentum is taken as the x-axis direction, the direction corresponding to the orbit radius of the source satellite is taken as the z-axis, and the direction of the y-axis is determined by the right-hand rule according to the directions of the x-axis and the z-axis to establish the Hill coordinate system. r m1z It only occurs in the satellite orbit plane (z direction). The vibration of the satellite platform will also cause radial displacement. The radial displacement caused by the vibration of the platform itself is considered to be two independently distributed radial displacements in the vertical direction (z direction) and the horizontal direction (y direction). Therefore, this embodiment obtains the first radial displacement caused by the external perturbation factor of the light beam emitted by the source satellite to the destination satellite r m1z And the second radial displacement caused by platform vibration. Among them, the first radial displacement occurs in the z direction of the Hill coordinate system, and obeys the expectation of 0 and the variance is The Gaussian distribution of ; The second radial displacement is two independent radial displacements occurring in the z and y directions of the Hill coordinate system r m2z and r m2y , and the two independent radial displacements are both expected to be 0, and the variance is The Gaussian distribution of , .

[0025] At this time, 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.

[0026] Assume that the source satellite and the destination satellite use Laguerre-Gaussian LG beams for OAM communication. LG beams are a type of beam commonly used in OAM communication. The light field expression of LG beams is: ; In the formula, 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 spatial point to the transmission axis; 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, w 0 is the initial beam waist radius; i is an imaginary unit; is the Rayleigh distance, and λ is the wavelength of light.

[0027] For fixed p LG beams are always orthogonal. For the convenience of research, p = 0, the light field distribution of the LG beam is: ; At the same time, according to the property that different modes of LG beams are orthogonal to each other, it can be known that: ; In the formula, l 1 and l 2 are the topological charges of vortex beams in different modes.

[0028] Then, the field intensity distribution of the light beam emitted by the source satellite under the influence of pointing error is: ; In the formula, is the optical axis offset angle.

[0029] From this formula It can be seen from the term that radial displacement will cause the phase change of the OAM wave. By performing Bessel series expansion on this term, the field intensity distribution formula of the light beam emitted by the source satellite under the influence of pointing error can be further converted into: ; In the formula, I m for m The modified Bessel function of the first kind, J n for n The first-order Bessel function formula shows that the phase change caused by radial displacement will further lead to crosstalk between OAM modes.

[0030] Step 103, expressing the field intensity distribution of the light beam under the influence of the pointing error as a form of spiral harmonic function expansion, and radially integrating the expansion coefficients in the form of spiral harmonic function expansion to obtain the energy of each OAM mode in the light beam.

[0031] Specifically, in order to facilitate subsequent derivation, this embodiment expresses the field intensity distribution of the light beam under the influence of the pointing error as an expansion of the spiral harmonic function, as shown in the following formula: ; In the formula, k is the number of OAM modes, is the expansion coefficient, expressed by the following formula: ; The energy of each OAM mode in the beam is obtained by radially integrating the expansion coefficients in the form of the helical harmonic function expansion, as follows: .

[0032] Step 104, 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.

[0033] In an example, this embodiment obtains the weight value of the energy of each OAM mode in the light beam to 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, and uses it as the purity of each OAM mode.

[0034] Among them, since the total energy of the entire beam can be expressed as: ; Then the weight of the energy of each OAM mode in the beam to the total energy of the entire beam can be calculated: .

[0035] In another example, this embodiment obtains the weight value of the energy of each OAM mode in the light beam to 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, and then obtains 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 according to the OAM intersatellite optical communication system model. Then, 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 emitted by the source satellite to the total power of the light beam received by the destination satellite.

[0036] Specifically, due to the different light intensity distributions in different modes, the power received by the receiver is different under different transmission OAM modes and pointing errors. In the case of larger transmission modes and larger pointing errors, the receiver cannot receive all the transmission power, so the power attenuation caused by the pointing error should also be considered. The power attenuation caused by the pointing error can be calculated by the total received power. Pr and total transmit power Pt The ratio of the total power of the beam emitted by the source satellite to the total power of the beam received by the destination satellite is expressed as: ; In the formula, , is the radial displacement r m =0 corresponding to the cylindrical coordinate system coordinates.

[0037] The purity of each OAM mode under the influence of the final pointing error is h It is expressed as: .

[0038] Next, the probability density function (PDF) and cumulative distribution function (CDF) of the purity of the OAM mode in the OAM intersatellite optical communication system are constructed by combining the purity of multiple OAM modes. In theory, the radial displacement of the target caused by the pointing error can be r mThe PDF of the corresponding OAM mode purity is obtained from the distribution, but the actual calculation involves the Hoyt distribution and the related integral operations of the Bessel series, and it is difficult to directly calculate the relevant closed-form expression. Therefore, this embodiment adopts a fitting scheme to describe the PDF of the OAM mode purity. Here, the PDF of the OAM mode purity under the influence of the pointing error is described in the form of a piecewise function. At this time, the PDF expression of the OAM purity can be expressed as follows: ; Furthermore, the cumulative distribution function of the OAM mode purity in the corresponding OAM intersatellite optical communication system can be derived: ; 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.

[0039] 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, and being able to provide the estimated error. 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: 1. Arrange the random data in ascending order [ X 1 , X N ], take from the middle spacing k points.

[0040] 2. The selected sample points can be expressed as , i =1… k .

[0041] 3. The probability corresponding to the selected sample points can be expressed as p i =N i / N . N i Corresponding to less than X i The amount of data.

[0042] 4. According to the formula F ( X i ) =pi . Use the least squares method to find the relevant parameters. The more points you take, the more accurate the parameters will be.

[0043] For the proposed PDF formula in the form of piecewise function, the values ​​of the break point θ are traversed from 0 to 1. After each value is taken, the point estimation method is used to solve the relevant parameters on the left and right sides of the break point, and the root mean square error (MSE) between the break point and the empirical PDF is recorded. Finally, the break point with the smallest MSE is the optimal break point, and the corresponding parameters are the optimal parameters.

[0044] For example, refer to Figures 3 to 6 It can be seen that the root mean square error between the fitted OAM intersatellite optical communication mode purity PDF under different OAM modes and pointing errors and the statistical PDF results is within 3×10 -6 The following shows that the proposed fitting PDF formula can well characterize the OAM mode purity distribution under the influence of pointing error. The CDF formula can also be verified by referring to the above scheme, which will not be repeated here.

[0045] Step 105 , 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.

[0046] Specifically, the probability density function and cumulative distribution function of the OAM mode purity in the OAM inter-satellite optical communication system are used to obtain the channel performance such as the interruption probability and ergodic capacity of the OAM inter-satellite optical communication system under the influence of pointing error, so as to evaluate the performance of the OAM inter-satellite optical communication system.

[0047] It can be understood that this embodiment determines the performance of the OAM inter-satellite optical communication system under the influence of the pointing error factor, and in practice, the performance of the OAM inter-satellite optical communication system under other different influencing factors can also be evaluated.

[0048] In this embodiment, a system model of an OAM intersatellite optical communication system is established when there is a pointing error between the source satellite and the destination satellite due to platform vibration and external perturbation factors, and 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, and the field intensity distribution of the light beam under the influence of the pointing error is expressed as a spiral harmonic function expansion form, and the expansion coefficient in the spiral harmonic function expansion form is radially integrated to obtain the energy of each OAM mode in the light beam, and then the purity of each OAM mode can be obtained according to the energy of each OAM mode in the light beam and the total energy of the entire light beam. Finally, the performance of the OAM intersatellite optical communication system is evaluated based on the probability density function and cumulative distribution function constructed based on the purity of multiple OAM modes. This scheme 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 judges the influence of the crosstalk between multiple OAM modes caused by the pointing error on the performance of the OAM intersatellite optical communication system based on this, and realizes the performance evaluation of the OAM intersatellite optical communication system under the influence of the pointing error.

[0049] This embodiment is applicable to OAM intersatellite optical communication scenarios, especially the analysis of the performance of OAM intersatellite optical communication systems under the influence of pointing errors, 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, through the combination with the prior art, the present invention is expected to achieve greater breakthroughs in the field of OAM intersatellite optical communication, and promote 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 intersatellite optical communication technology, but also brings more advanced and reliable solutions for deep space OAM optical communication.

[0050] The step division of the various methods above is only for clear description. When implemented, they can be combined into one step or some steps can be split and decomposed 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 without changing the core design of the algorithm and process are all within the protection scope of the invention.

[0051] Another embodiment of the present invention relates to an OAM inter-satellite optical communication system performance evaluation system. The implementation details of the OAM inter-satellite optical communication system performance evaluation system of this embodiment are specifically described below. The following content is only for the convenience of understanding the implementation details provided, and is not necessary for implementing this solution. The OAM inter-satellite optical communication system performance evaluation system of this embodiment includes: 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; The performance evaluation module is used to evaluate 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.

[0052] 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 conjunction with the above method embodiment. The relevant technical details and technical effects mentioned in the above embodiment are still valid in this embodiment, and in order to reduce repetition, they are not repeated here. Accordingly, the relevant technical details mentioned in this embodiment can also be applied in the above embodiment.

[0053] It is worth mentioning that all modules involved in this embodiment are logic modules. In practical applications, a logic unit can be a physical unit, a part of a physical unit, or a combination of multiple physical units. In addition, in order to highlight the innovative part of the present invention, this embodiment does not introduce units that are not closely related to solving the technical problem proposed by the present invention, but this does not mean that there are no other units in this embodiment.

[0054] Another embodiment of the present invention relates to a computer device, comprising: 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 in the above-mentioned embodiments.

[0055] Among them, the memory and the processor are connected in a bus manner, and the bus may include any number of interconnected buses and bridges, and the bus connects various circuits of one or more processors and memories together. The bus can also connect various other circuits such as peripherals, voltage regulators, and power management circuits, which are well known in the art and are therefore not further described herein. The bus interface provides an interface between the bus and the transceiver. The transceiver can be one element or multiple elements, such as multiple receivers and transmitters, providing a unit for communicating with various other devices on a transmission medium. The data processed by the processor is transmitted on a wireless medium via an antenna, and further, the antenna also receives data and transmits the data to the processor.

[0056] The processor is responsible for managing the bus and general processing, and can also provide various functions, including timing, peripheral interfaces, voltage regulation, power management, and other control functions. Memory can be used to store data used by the processor when performing operations.

[0057] Another embodiment of the present invention relates to a computer-readable storage medium storing a computer program, which implements the above method embodiment when executed by a processor.

[0058] That is, those skilled in the art can understand that all or part of the steps in the above-mentioned embodiment method can be completed by instructing the relevant hardware through a program, and the program is stored in a storage medium, including a number of instructions to enable a device (which can be a single-chip microcomputer, chip, etc.) or a processor to perform all or part of the steps of the method described in each embodiment of the present invention. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (Read-Only Memory, referred to as: ROM), random access memory (Random Access Memory, referred to as: RAM), disk or optical disk and other media that can store program codes.

[0059] Those skilled in the art will appreciate that the above embodiments are specific embodiments for implementing the present invention, and in actual applications, various changes may be made thereto in form and detail 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 the OAM inter-satellite optical communication system is evaluated through the probability density function and cumulative distribution function of the OAM mode purity in the OAM inter-satellite optical communication system.

2. The OAM intersatellite optical communication system performance evaluation method according to claim 1, characterized in that: The method of 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 of the light beam emitted by the source satellite to the destination satellite due to external perturbations r 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 occurring in the z direction and y direction of the Hill coordinate system r 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 obeys 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.

3. The OAM intersatellite optical communication system performance evaluation method according to claim 2, 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: ； In the formula, 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 spatial point to the transmission axis; 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, w 0 is the initial beam waist radius; i is an imaginary unit; is the Rayleigh distance, λ is the wavelength of light; make 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: ； In the formula, l 1 and l 2 are the topological charges of vortex beams of different modes; The field intensity distribution of the light beam emitted by the source satellite under the influence of pointing error is: ； In the formula, is the optical axis offset angle.

4. The OAM intersatellite optical communication system performance evaluation method according to claim 3, 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: ； In the formula, k is the number of OAM modes, is the expansion coefficient, 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: 。 5. The OAM intersatellite optical communication system performance evaluation method according to claim 4, 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.

6. The OAM intersatellite optical communication system performance evaluation method according to claim 5, 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 of the beam received by the destination satellite The total power of the beam emitted by the source satellite The ratio is: ； In the formula, r 0 , is the radial displacement r m =0 corresponding cylindrical coordinates; The purity of each OAM mode is: ； 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: ； 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.

7. 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.

8. 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; The performance evaluation module is used to evaluate 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.

9. 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 7.

10. 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 7 is implemented.

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