Satellite-to-ground coherent optical communication multi-aperture receiving performance evaluation method

Abstract

The invention discloses a satellite-ground coherent optical communication multi-aperture receiving performance evaluation method, which belongs to the field of high-speed satellite-ground laser communication, and comprises the following steps: generating a multi-layer Non-Kolmogorov turbulence phase screen by adopting a power spectrum inversion method added with subharmonic compensation; adopting an equal Rytov index spacing method to sort the multiple layers of phase screens to form multiple layers of non-equidistant phase screens; a distributed optical transmission theory is adopted to simulate and analyze the total mixing efficiency value of laser transmission between the satellite and the ground; and analyzing the bit error rate. By fully, truly and accurately simulating the real and non-uniform satellite-ground atmospheric turbulence characteristics, the satellite-ground communication evaluation is more accurate, and a technical reference is provided for the field of high-speed satellite-ground laser communication in the new-generation information technology industry.

Description

Technical Field

[0001] The invention relates to the field of high-speed satellite-to-ground laser communication, and in particular to a method for evaluating multi-aperture receiving performance of satellite-to-ground coherent optical communication. Background Art

[0002] With the development of space information technology, the demand for satellite-to-ground communication bandwidth continues to escalate. Free-space optical communication technology has become the focus of current research and application due to its large bandwidth and high confidentiality. Space laser communication technology can be divided into incoherent optical communication technology and coherent optical communication technology according to the modulation method. Coherent optical communication technology has significant advantages in ultra-high-speed and long-distance communication applications due to its advantages such as large bandwidth, high detection sensitivity and good background noise suppression ability.

[0003] Laser transmission between satellite and ground will be affected by atmospheric turbulence, which will in turn affect the performance of bit error rate, signal-to-noise ratio, interruption probability, etc. in communication, seriously affecting the quality of laser transmission. Multi-aperture receiving technology in spatial diversity technology can alleviate the negative impact of atmospheric turbulence on satellite-to-ground coherent optical communication systems. At the same time, outdoor experiments on satellite-to-ground coherent optical communications are costly and difficult, and numerical simulation methods have become a common method for simulating communication links and establishing optical systems.

[0004] In the patent document with publication number CN116488737A, a space optical communication system including a multi-aperture receiving device is provided. In the patent document with publication number CN117376157A, a simulation method of multi-aperture receiving technology applied in the field of atmospheric laser communication is provided. At present, there is still no reliable method to evaluate the communication performance of coherent optical communication multi-aperture receiving systems. In the paper "Satellite-to-ground optical downlink model using modemismatching multi-mode photonic lanterns", Guo et al. constructed a von-Karman turbulence numerical simulation model to simulate the atmospheric turbulence effects between the satellite and the ground within 0-20km. In the paper "Channel Correlation Influence on Spatial Diversity Optical Key Generation", Li Hui et al. established a satellite-to-ground laser communication channel model based on Kolmogorov turbulence theory to explore the influence of the spatial diversity atmospheric optical channel key generation system on the space optical communication system. The atmospheric turbulence simulation models between satellites and ground stations in the above papers are all based on the theory of uniform atmospheric turbulence. However, the real atmospheric turbulence between the satellite and the ground has non-uniform characteristics, which conforms to the Non-Kolmogorov turbulence theory, and the turbulence intensity in the entire satellite-to-ground link is different. Therefore, the use of uniform atmospheric turbulence theory does not conform to the real characteristics of atmospheric turbulence between the satellite and the ground, and it is easy to cause undersampling in strong turbulence areas and oversampling in weak turbulence areas, and it is impossible to accurately describe the atmospheric turbulence effects between the satellite and the ground.

[0005] Currently, there is a lack of performance evaluation methods for multi-aperture reception in satellite-to-ground laser communications. In addition, most existing numerical simulation models of atmospheric turbulence in satellite-to-ground laser communication systems assume that the turbulence is uniform on the propagation path, which is inconsistent with the actual situation. As a result, there are large errors between the numerical simulation results and the actual non-uniform atmospheric turbulence environment between the satellite and the ground. Summary of the invention

[0006] The technical problem to be solved by the present invention is to provide a method for evaluating the multi-aperture receiving performance of satellite-to-ground coherent optical communication. The method aims to solve the problem that the current research cannot accurately simulate the atmospheric turbulence effect between satellite and ground and lacks reliable evaluation of the multi-aperture receiving performance of satellite-to-ground coherent optical communication, and can accurately describe the atmospheric turbulence effect between the satellite and the ground and evaluate the performance of satellite-to-ground coherent optical communication.

[0007] In order to solve the above technical problems, the technical solution adopted by the present invention is: a method for evaluating the multi-aperture receiving performance of satellite-to-ground coherent optical communication, comprising the following steps:

[0008] Step 1: Generate a multi-layer Non-Kolmogorov turbulence phase screen using the power spectrum inversion method with subharmonic compensation;

[0009] Step 2: Use the equal Rytov index interval method to sort the multi-layer phase screens to form multi-layer non-equidistant phase screens;

[0010] Step 3: Use the distributed light transmission theory to simulate the transmission of laser between satellite and ground;

[0011] Step 4: Analyze the overall mixing efficiency value;

[0012] Step 5: Analyze the bit error rate.

[0013] The further improvement of the technical solution of the present invention is that: the specific steps of step 1 are as follows:

[0014] Without considering the inner and outer scales of turbulence, the three-dimensional power spectrum of Non-Kolmogorov turbulence is Φ n The specific expression is:

[0015]

[0016]

[0017] Where: α 1 , α 2 , α 3 are the turbulence spectrum power laws of the boundary layer, troposphere, and stratosphere, respectively, k r is the spatial wave function, L is the total transmission distance, h is the height from the ground, C n 2(h) is the height distribution model of the refractive index structure constant, and its specific expression is:

[0018]

[0019] Where: A = 1.7 × 10 -14 [m -2 / 3 ], v = 21 [m / s] is the wind speed near the ground;

[0020] Use the power spectral density function to filter a complex Gaussian random matrix with a mean of 0 and a variance of 1, and perform an inverse Fourier transform on the filtered function to obtain the high-frequency component of the random phase screen. Based on Fourier low-frequency harmonic resampling, low-frequency harmonic compensation is generated by interpolation and merging The random phase screen expression is:

[0021]

[0022] The further improvement of the technical solution of the present invention is that the specific steps of step 2 are as follows:

[0023] Step 2.1: Set a constant c;

[0024] Step 2.2: Establish the identity σ R 2 (Δz i )≡c, where σ R 2 (Δz i )=1.23C n 2 (z i ) 7 / 6 (Δz i ) 11 / 6 , k = 2π / λ, Δz i is the distance between the i-th phase screen and the i+1-th phase screen;

[0025] Step 2.3: According to the identity 1.23C n 2 (0)k 7 / 6 (Δz 1 ) 11 / 6 ≡c, turbulent refractive index structure constant C near the ground n 2 (0) and constant c to calculate the height Δz of the first phase screen 1 ;

[0026] Step 2.4: According to the identity 1.23C n 2 (z i ) 7 / 6 (Δz i) 11 / 6 ≡c, turbulent refractive index structure constant C at the height corresponding to the i-th phase screen n 2 (z i ) and constant c to calculate each Δz i ;

[0027] Step 2.5: Repeat step 2.4 until the phase screen accumulation interval is equal to the total transmission distance.

[0028] The further improvement of the technical solution of the present invention is that the specific steps of step 3 are as follows:

[0029] The atmospheric channel is represented as a series of turbulent phase screens, and then a random phase is introduced to each phase screen. Finally, the Huygens-Fresnel theory is used to simulate the interaction between the phase screens. The transmission process of the light beam on the turbulent path can be expressed as:

[0030]

[0031] Where: F -1 {·} represents the inverse Fourier transform, k x and k y denote the components of the wave function in the x and y directions respectively.

[0032] The further improvement of the technical solution of the present invention is that the specific steps of step 4 are as follows:

[0033] Step 4.1: Calculate the mixing efficiency of each aperture. The specific expression is:

[0034]

[0035] Where: i represents the i-th aperture, A L,i A represents the amplitude of the local oscillator light received by the i-th aperture, S,i represents the amplitude of the signal light received by the i-th aperture, represents the spatial phase difference between the local oscillator light and the signal light received by the i-th aperture, and S is the mixing area of ​​the signal light;

[0036] Step 4.2: Sum the mixing efficiencies of each aperture and take the average to calculate the overall mixing efficiency of the multi-aperture receiving system. The specific expression is:

[0037]

[0038] Where: m is the total number of pores.

[0039] The further improvement of the technical solution of the present invention is that the specific steps of step 5 are as follows:

[0040] The bit error rate is used to quantitatively evaluate the impact of satellite-ground atmospheric turbulence on multi-aperture reception in coherent optical communication. The specific expression is:

[0041]

[0042] Where: erfc(·) is the complementary error function, η is the quantum efficiency of the photodetector, N p is the number of photons received within a single bit.

[0043] Due to the adoption of the above technical scheme, the technical progress achieved by the present invention is: by adopting the power spectrum inversion method with subharmonic compensation to generate multi-layer Non-Kolmogorov turbulence phase screens; by adopting the equal Rytov index interval method to sort the multi-layer phase screens to form multi-layer non-equidistant phase screens, the distributed optical transmission theory is used to simulate the transmission of lasers between the satellite and the ground, which can fully and accurately simulate the real non-uniform atmospheric turbulence characteristics between the satellite and the ground. By using the mixing efficiency and bit error rate to evaluate the communication reception performance, a quantitative evaluation can be made, and the evaluation is more accurate, providing a technical reference for the field of high-speed satellite-to-ground laser communication in the new generation of information technology industry. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative work.

[0045] Figure 1 It is an overall block diagram of the satellite-to-ground coherent optical communication multi-aperture receiving system of the present invention;

[0046] Figure 2 It is a flow chart of the method for evaluating multi-aperture receiving performance of satellite-to-ground coherent optical communication of the present invention; DETAILED DESCRIPTION

[0047] The present invention is further described in detail below in conjunction with embodiments:

[0048] like Figure 1The figure shows an overall block diagram of a satellite-to-ground coherent optical communication multi-aperture receiving system, including an interconnected satellite-to-ground laser transmission simulation module and a multi-aperture receiving coherent optical communication performance analysis module. The satellite-to-ground laser transmission simulation module generates multiple layers of non-equidistant turbulence phase screens based on the real satellite-to-ground atmospheric turbulence characteristics, and uses the distributed optical transmission theory to simulate the transmission between the satellite and the ground. The satellite-to-ground laser transmission simulation module includes a satellite-to-ground atmospheric turbulence simulation unit and a laser transmission simulation unit, wherein the satellite-to-ground atmospheric turbulence simulation unit generates multiple layers of non-equidistant Non-Kolmogorov turbulence phase screens to simulate the satellite-to-ground atmospheric turbulence effects, and the laser transmission simulation unit uses the distributed transmission theory to simulate the transmission of laser in the satellite-to-ground atmospheric turbulence. The multi-aperture receiving coherent optical communication performance analysis module includes a mixing efficiency analysis unit and a bit error rate analysis unit, which are used to study and analyze the mixing efficiency and bit error rate of multi-aperture receiving of satellite-to-ground coherent optical communication, respectively.

[0049] like Figure 2 FIG. 1 is a flow chart of a method for evaluating the multi-aperture receiving performance of satellite-to-ground coherent optical communication using the above-mentioned receiving system to realize communication evaluation, and includes the following steps:

[0050] Step 1: Generate a multi-layer Non-Kolmogorov turbulence phase screen using the power spectrum inversion method with subharmonic compensation. When the inner and outer scales of the turbulence are not considered, the power spectrum of Non-Kolmogorov turbulence is n The specific expression is as follows:

[0051]

[0052] Where: α 1 , α 2 , α 3 are the turbulence spectrum power laws of the boundary layer, troposphere, and stratosphere, respectively, and k r is the spatial wave function, L is the total transmission distance, h is the height from the ground, is the height distribution model of the refractive index structure constant, and its specific expression is:

[0053]

[0054] Where: A = 1.7 × 10 -14 [m -2 / 3 ], v=21[m / s] is the near-ground wind speed.

[0055] Use the power spectral density function to filter a complex Gaussian random matrix with a mean of 0 and a variance of 1, and perform an inverse Fourier transform on the filtered function to obtain the high-frequency component of the random phase screen. Based on Fourier low-frequency harmonic resampling, low-frequency harmonic compensation is generated by interpolation and merging The phase screen expression is:

[0056]

[0057] The above are the steps involved in generating the Non-Kolmogorov turbulence phase screen. The various parameters can be set according to the specific situation, for example: the power law of the boundary layer turbulence spectrum α 1 , tropospheric spectrum power law α 2 , Stratospheric spectrum power law α 3 Can be set to 11 / 3, 3.33, 3.75 respectively.

[0058] The phase structure function is used to evaluate the accuracy of the generated random phase screen. The phase structure function describes the statistical characteristics of the wavefront phase. Its specific expression is:

[0059]

[0060] Step 2: Use the equal Rytov index interval method to sort the multi-layer phase screens to form multi-layer non-equidistant phase screens;

[0061] Step 2.1: Set a constant c;

[0062] Step 2.2: Establish the identity σ R 2 (Δz i )≡c, where σ R 2 (Δz i )=1.23C n 2 (z i ) 7 / 6 (Δz i ) 11 / 6 , k = 2π / λ, Δz i is the distance between the i-th phase screen and the i+1-th phase screen;

[0063] Step 2.3: According to the identity 1.23C n 2 (0)k 7 / 6 (Δz 1 ) 11 / 6 ≡c, turbulent refractive index structure constant C near the ground n 2 (0) and constant c to calculate the height Δz of the first phase screen 1 ;

[0064] Step 2.4: According to the identity 1.23C n 2 (z i ) 7 / 6 (Δz i) 11 / 6 ≡c, turbulent refractive index structure constant C at the height corresponding to the i-th phase screen n 2 (z i ) and constant c to calculate each Δz i ;

[0065] Step 2.5: Repeat step 2.4 until the phase screen accumulation interval is equal to the total transmission distance.

[0066] The constant c determines the number and position of the multi-layer phase screen, and can be set according to the specific situation. For example, when the constant c is set to 0.00268, the number of phase screen layers within 0 to 20 kilometers is 20.

[0067] Step 3: Use the distributed light transmission theory to simulate the transmission of lasers between the satellite and the ground; first, represent the atmospheric channel as a series of turbulent phase screens, then introduce a random phase to each phase screen, and finally use the Huygens-Fresnel theory to simulate the interaction between phase screens. The transmission process of the light beam on the turbulent path can be expressed as:

[0068]

[0069] Where: F -1 {·} represents the inverse Fourier transform, k x and k y denote the components of the wave function in the x and y directions respectively.

[0070] In this step, the Gamma-Gamma distribution is compared with the light intensity probability distribution obtained by simulation to determine the accuracy of the laser transmission simulation unit. The specific expression of the Gamma-Gamma distribution is:

[0071]

[0072] Where: K α-β It is a second-kind modified Bessel function with parameters α-β, where parameters α and β are the large-scale flicker index and the small-scale flicker index, respectively.

[0073] Step 4: Analyze the overall mixing efficiency value; Step 4.1: Calculate the mixing efficiency of each aperture, the specific expression is:

[0074]

[0075] Where: i represents the i-th aperture, A L,i A represents the amplitude of the local oscillator light received by the i-th aperture, S,i represents the amplitude of the signal light received by the i-th aperture, represents the spatial phase difference between the local oscillator light and the signal light received by the i-th aperture, and S is the mixing area of ​​the signal light;

[0076] Step 4.2: Sum the mixing efficiencies of each aperture and take the average to calculate the overall mixing efficiency of the multi-aperture receiving system. The specific expression is:

[0077]

[0078] Where: m is the total number of pores.

[0079] Step 5: Analyze the bit error rate. The bit error rate is used to quantitatively evaluate the impact of satellite-ground atmospheric turbulence on coherent optical communication multi-aperture reception. The specific expression is:

[0080]

[0081] Where: erfc(·) is the complementary error function, η is the quantum efficiency of the photodetector, N p is the number of photons received within a single bit.

[0082] The present invention firstly simulates the satellite-to-ground atmospheric turbulence effect through the satellite-to-ground atmospheric turbulence simulation unit in the satellite-to-ground laser transmission module, then simulates the laser transmission between the satellite and the ground through the laser transmission simulation unit, and finally uses the mixing efficiency analysis unit and the bit error rate analysis unit in the multi-aperture receiving coherent optical communication performance analysis module to evaluate the quantitative influence of the satellite-to-ground atmospheric turbulence effect on the performance of the multi-aperture receiving coherent optical communication system, providing a technical reference for the field of high-speed satellite-to-ground laser communication in the new generation of information technology industry.

[0083] The embodiments described above are merely descriptions of preferred implementation modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for evaluating multi-aperture receiving performance of satellite-to-ground coherent optical communication, characterized in that: The steps include: Step 1: Generate a multi-layer Non-Kolmogorov turbulence phase screen using the power spectrum inversion method with subharmonic compensation; Step 2: Use the equal Rytov index interval method to sort the multi-layer phase screens to form multi-layer non-equidistant phase screens; Step 3: Use the distributed light transmission theory to simulate the transmission of laser between satellite and ground; Step 4: Analyze the overall mixing efficiency value; Step 5: Analyze the bit error rate.

2. The method for evaluating multi-aperture receiving performance of satellite-to-ground coherent optical communication according to claim 1, characterized in that: Step 1 The specific steps are as follows: Without considering the inner and outer scales of turbulence, the three-dimensional power spectrum of Non-Kolmogorov turbulence is Φ n The specific expression is: Where: α1, α2, α3 are the turbulence spectrum power laws of the boundary layer, troposphere, and stratosphere, respectively, and k r is the spatial wave function, L is the total transmission distance, h is the height from the ground, C n 2 (h) is the height distribution model of the refractive index structure constant, and its specific expression is: Where: A = 1.7 × 10 -14 [m -2 / 3 ], v = 21 [m / s] is the wind speed near the ground; Use the power spectral density function to filter a complex Gaussian random matrix with a mean of 0 and a variance of 1, and perform an inverse Fourier transform on the filtered function to obtain the high-frequency component of the random phase screen. Based on Fourier low-frequency harmonic resampling, low-frequency harmonic compensation is generated by interpolation and merging The random phase screen expression is:

3. The method for evaluating multi-aperture receiving performance of satellite-to-ground coherent optical communication according to claim 1, characterized in that: Step 2 The specific steps are as follows: Step 2.1: Set a constant c; Step 2.2: Establish the identity σ R 2 (Δz i )≡c, where σ R 2 (Δz i )=1.23C n 2 (z i ) 7 / 6 (Δz i ) 11 / 6 , k = 2π / λ, Δz i is the distance between the i-th phase screen and the i+1-th phase screen; Step 2.3: According to the identity 1.23C n 2 (0)k 7 / 6 (Δz1) 11 / 6 ≡c, turbulent refractive index structure constant C near the ground n 2 (0) and constant c to calculate the height Δz1 of the first phase screen; Step 2.4: According to the identity 1.23C n 2 (z i ) 7 / 6 (Δz i ) 11 / 6 ≡c, turbulent refractive index structure constant C at the height corresponding to the i-th phase screen n 2 (z i ) and constant c to calculate each Δz i ; Step 2.5: Repeat step 2.4 until the phase screen accumulation interval is equal to the total transmission distance.

4. The method for evaluating multi-aperture receiving performance of satellite-to-ground coherent optical communication according to claim 1, characterized in that: Step 3 The specific steps are as follows: The atmospheric channel is represented as a series of turbulent phase screens, and then a random phase is introduced to each phase screen. Finally, the Huygens-Fresnel theory is used to simulate the interaction between the phase screens. The transmission process of the light beam on the turbulent path can be expressed as: Where: F -1 {·} represents the inverse Fourier transform, k x and k y denote the components of the wave function in the x and y directions respectively.

5. The method for evaluating multi-aperture receiving performance of satellite-to-ground coherent optical communication according to claim 1, characterized in that: Step 4 The specific steps are as follows: Step 4.1: Calculate the mixing efficiency of each aperture. The specific expression is: Where: i represents the i-th aperture, A L,i A represents the amplitude of the local oscillator light received by the i-th aperture, S,i represents the amplitude of the signal light received by the i-th aperture, represents the spatial phase difference between the local oscillator light and the signal light received by the i-th aperture, and S is the mixing area of ​​the signal light; Step 4.2: Sum the mixing efficiencies of each aperture and take the average to calculate the overall mixing efficiency of the multi-aperture receiving system. The specific expression is: Where: m is the total number of pores.

6. The method for evaluating multi-aperture receiving performance of satellite-to-ground coherent optical communication according to claim 1, characterized in that: Step 5 The specific steps are as follows: The bit error rate is used to quantitatively evaluate the impact of satellite-ground atmospheric turbulence on multi-aperture reception in coherent optical communication. The specific expression is: Where: erfc(·) is the complementary error function, η is the quantum efficiency of the photodetector, N p is the number of photons received within a single bit.

Images