Optical and electrical integrated space optical communication multi-aperture receiving method

Abstract

The invention provides a space optical communication multi-aperture receiving method based on optical and electrical comprehensive synthesis. The number of optical beam combination sub-apertures is intelligently adjusted by adopting densely-arranged multi-aperture optical antennas so as to ensure that light paths and light signals after beam combination are mutually independent; receiving of optical signals and correction of first-order and second-order Zernike aberration are achieved through the optical antenna array with the total number of sub-apertures determined on the basis of the receiving plane; the optical signals pass through the optical beam splitter, one part of the optical signals are input into the coupling energy photoelectric detector to be converted into voltage or current feedback signals to be input into the control module, and the other part of the optical signals are input into the N * 1 self-adaptive light beam synthesis module; coherent beam combination is carried out on the optical signals through the N * 1 adaptive beam combination module to form M paths of mutually independent optical signals; and carrying out direct detection or coherent detection on the M paths of optical signals, converting the M paths of optical signals into M paths of electric signals, and carrying out electrical signal synthesis on the M paths of electric signals. The communication stability is improved, and the independence of the electrical synthesis signal is ensured.

Description

Technical Field

[0001] The present invention relates to the technical field of MIMO free-space optical communication, and particularly to a multi-aperture receiving method for space optical communication that comprehensively synthesizes optics and electricity. Background Art

[0002] Free-space optical communication (FSOC) has been favored by people for its excellent high speed and energy-saving performance. Compared with millimeter-wave communication, FSOC has higher bandwidth and lower power consumption. Compared with fiber-optic communication, high-bandwidth FSOC is not affected by the inter-symbol interference problem caused by the fiber dispersion effect. However, low-order aberrations represented by the first and second-order Zernike aberrations in the atmosphere will limit the receiving effect of FSOC, increasing the bit error rate or even causing communication interruption. Adopting a multi-aperture receiving scheme to receive optical signals and correct the first and second-order Zernike aberrations can effectively reduce the interruption probability and improve the communication performance.

[0003] At present, the multi-path sub-signal synthesis methods of the space optical communication multi-aperture receiving scheme mainly include electrical synthesis and optical synthesis. The electrical synthesis method includes analog combining methods represented by combiners and digital combining methods represented by algorithms such as maximum ratio combining (MRC), equal gain combining (EGC), and selection combining (SC). However, each path of electrical synthesis requires a separate detector and requires the sub-channels to be independent, wasting a large amount of energy in the receiving plane. Optical synthesis compensates the phases of multiple input optical signals, pre-synthesizes a beam of optical signals before signal demodulation, and then performs detection and demodulation. Optical synthesis can effectively improve the power of optical signals, increase the optical signal-to-noise ratio in a strong turbulence environment, and thus suppress optical intensity scintillation, which is a feasible solution for future ultra-high throughput transmission communication requirements.

[0004] However, currently considering the electrical synthesis method, only when the sub-apertures are independent, the performance will become better as the number of sub-apertures increases. Therefore, how to improve the receiving efficiency of the multi-aperture antenna while ensuring the independence of the electrical combined signals is a problem that needs to be solved currently. Summary of the Invention

[0005] Aiming at the deficiencies in the prior art, the present invention provides a multi-aperture receiving method for space optical communication that comprehensively synthesizes optics and electricity to solve the technical problem of how to ensure the independence of the electrical synthesis signals in the multi-aperture receiving in the prior art.

[0006] The present invention provides a multi-aperture receiving method for space optical communication that comprehensively synthesizes optics and electricity, including:

[0007] S1. Determine the total receiving area according to the aperture size of the closely-packed multi-aperture optical antenna, the communication link length, and the turbulence intensity;

[0008] S2. Intelligently adjust the number of sub-apertures of the optical beam combiner in combination with the atmospheric refractive index structure constant, communication link length, signal light wavelength, and channel correlation coefficient to ensure that the combined optical signals are independent of each other, and perform coupled reception of the optical signals and correction of the first and second order Zernike aberrations based on the densely packed multi-aperture optical antenna that determines the receiving area and the number of sub-apertures;

[0009] S3. The optical signal passes through an optical beam splitter, and a part of the optical signal is input to a coupled energy photodetector to be converted into a voltage or current feedback signal and input to a control module, and the energy of the other part of the optical signal is input to an N×1 adaptive optical beam synthesis module;

[0010] S4. Based on the intelligently adjusted N×M sub-apertures, the optical signal is coherently combined into one optical signal through the N×1 adaptive optical beam synthesis module, and finally M independent optical signals are formed in total;

[0011] S5. Perform direct detection or coherent detection on the M optical signals, convert them into M electrical signals, electrically synthesize the M electrical signals into one electrical signal through electrical synthesis, and perform decision demodulation on the electrical signal.

[0012] Optionally, the densely packed multi-aperture optical antenna includes:

[0013] The densely packed multi-aperture optical antenna uses an adaptive fiber coupler array or an on-chip phased array to realize the beam splitting and combining functions of the optical path.

[0014] Optionally, intelligently adjusting the number of sub-apertures of the optical beam combiner in combination with the atmospheric refractive index structure constant, communication link length, signal light wavelength, and channel correlation coefficient includes:

[0015] When the correlation coefficient between two sub-apertures is less than 1 / e 2 it can be regarded as an independent channel, and the channel correlation coefficient between two points on the receiving plane in the densely packed multi-aperture optical antenna:

[0016]

[0017] where i and j respectively represent two sub-apertures, s ij is the distance between the centers of the two sub-apertures, are the scintillation indices at the i and j sub-apertures respectively, and C ij is the covariance coefficient between the two sub-apertures.

[0018] Optionally, the intelligently adjusting the number of sub-apertures of the optical beam combiner in combination with the atmospheric refractive index structure constant, communication link length, signal light wavelength, and channel correlation coefficient further includes:

[0019] Based on the covariance of irradiance being a function of the distance s, in a weak turbulence environment, the covariance function of light intensity is:

[0020]

[0021] In a strong turbulence environment, the covariance function of the optical intensity is as follows:

[0022]

[0023]

[0024] Wherein, is the Rytov variance, and L is the communication link length.

[0025] Optionally, the coupled energy photodetector includes:

[0026] A photon detector, a photodiode, a phototransistor, an avalanche photodiode or a photomultiplier tube that realizes the conversion of an optical signal into a voltage or current signal.

[0027] Optionally, the N×1 adaptive beam combining module includes:

[0028] The N×1 adaptive beam combining module is composed of a synthesis phase modulator, a directional coupler, a synthesis photodetector and a synthesis piston aberration controller, and is used to compensate for the piston aberration between the adaptive fiber coupler arrays.

[0029] Optionally, the electrical signal synthesis of the M electrical signals includes:

[0030] The electrical signal synthesis of the M electrical signals is performed by using equal gain combining and maximum signal-to-noise ratio combining algorithms.

[0031] Optionally, the adaptive fiber coupler array includes:

[0032] The arrangement of the adaptive fiber coupler array is triangular, square, hexagonal, circular or annular; and the overall receiving aperture and transmitting aperture can be increased by increasing the number of adaptive fiber couplers.

[0033] Optionally, the control module includes:

[0034] A multi-channel adaptive fiber coupler, which is used to generate an output control voltage by using a stochastic gradient descent algorithm, a dithering algorithm, a deep learning algorithm or a reinforcement learning algorithm

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] By intelligently adjusting the number of apertures of the optical beam combiner, the energy waste caused by independent apertures can be avoided, different atmospheric turbulence conditions can be coped with, and the communication stability can be improved. Through the multi-aperture receiving method of comprehensive optical and electrical synthesis, the independence of the electrical synthesis signal is ensured by pre-using optical coherent beam combination. When the aperture array is expanded with a larger number of units on a large scale, the complexity of the electrical signal processing part is reduced, and the optical intensity of the single-channel detection signal is increased through optical synthesis, so that the modulated optical signal can still be correctly demodulated by the electrical synthesis algorithm under low signal-to-noise ratio conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The accompanying drawings herein are incorporated into the specification and constitute a part of this specification, showing embodiments consistent with the present invention, and are used together with the specification to explain the principles of the present invention.

[0038] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the accompanying drawings required for the description of the embodiments or the prior art. Obviously, for those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0039] Figure 1 It is a schematic flowchart of the present invention;

[0040] Figure 2 It is a general schematic diagram of the optoelectronic comprehensive synthesis scheme in the present invention;

[0041] Figure 3 It is a schematic diagram of the spatial diversity array distribution within the same receiving range in the present invention;

[0042] Figure 4 It is a general schematic diagram of the optical synthesis scheme in the present invention;

[0043] Figure 5 It is a general schematic diagram of the electrical synthesis scheme in the present invention;

[0044] Figure 6 It is a schematic diagram showing the influence relationship between the antenna receiving aperture and the number of sub-apertures of the vertical link on the optical signal scintillation index in the present invention;

[0045] Figure 7 It is a schematic diagram showing the influence relationship between the number of sub-apertures within the same receiving range in the horizontal link on the turbulence suppression performance in the present invention;

[0046] Figure 8 It is a schematic diagram of the synthesis path of each received signal in the present invention;

[0047] Figure 9Schematic diagram of the outage probability comparison of different receiving schemes such as optical and electrical comprehensive synthesis, electrical synthesis, and optical synthesis under different channel lengths obtained through simulation. Detailed implementation manners

[0048] To make the objectives, technical solutions, and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are some but not all of the embodiments of the present application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present application without creative efforts shall fall within the protection scope of the present application. In the embodiments of the present invention, functional units with the same reference numerals have the same and similar structures and functions.

[0049] Refer to Figure 1 and Figure 2 , the present invention provides a multi-aperture receiving method for space optical communication with optical and electrical comprehensive synthesis, including:

[0050] S1. Determine the total receiving area according to the aperture size, communication link length, and turbulence intensity of the closely packed multi-aperture optical antenna;

[0051] S2. Intelligently adjust the number of optical beam combining sub-apertures in combination with the atmospheric refractive index structure constant, communication link length, signal light wavelength, and channel correlation coefficient to ensure that the combined optical signals are independent of each other, and perform coupled reception of the optical signals and correction of the first and second order Zernike aberrations based on the closely packed multi-aperture optical antenna with the determined receiving area and number of sub-apertures;

[0052] S3. The optical signal passes through an optical beam splitter, and a part of the optical signal is input to a coupled energy photodetector to be converted into a voltage or current feedback signal and input to a control module, and the energy of the other part of the optical signal is input to an N×1 adaptive beam synthesis module;

[0053] S4. Based on the intelligently adjusted N×M sub-apertures, the optical signal is coherently combined into one optical signal through the N×1 adaptive beam synthesis module, and finally M independent optical signals are formed in total;

[0054] S5. Perform direct detection or coherent detection on the M optical signals, convert them into M electrical signals, merge the M electrical signals through electrical processing and output them as one electrical signal, and perform decision demodulation on the electrical signal.

[0055] In this embodiment, S1. Determine the total receiving area according to the aperture size, communication link length, and turbulence intensity of the closely packed multi-aperture optical antenna;

[0056] Determine the total receiving area based on the transmission path distance and the atmospheric turbulence intensity, determine the size of the sub-aperture based on the atmospheric refractive index structure constant, the communication link length, and the signal light wavelength, and determine the layout pattern of the multi-aperture receiving array based on the principle of close-packed distribution; and evaluate the receiving performance of the antenna based on the scintillation index and the aperture averaging coefficient of the optical signal.

[0057] The scintillation index of the optical signal reflects the change of the normalized optical intensity, and the scintillation index is defined as:

[0058]

[0059] where I is the magnitude of the normalized optical intensity. Generally, the magnitude of the scintillation index is:

[0060]

[0061] where the Rytov variance refers to the variance of the logarithm of the optical intensity.

[0062] The communication link can be divided into a satellite-ground vertical link and a ground horizontal link. The turbulence intensity of the entire link is the integral of the atmospheric refractive index structure constant on the path. According to the atmospheric stratification theory, it is known that only in the area with a large temperature difference near the ground surface is the atmospheric turbulence more serious. The turbulence intensity of all paths of the ground horizontal link is affected by the ground atmospheric conditions. Therefore, the turbulence intensity of the vertical link and the horizontal link is different.

[0063] Reference Figure 6 It can be seen that in the vertical link, if the area D of the total receiving aperture is changed G , when the turbulence is strong , when the aperture size is increased from 0.1 m to 1 m, the scintillation index of a single-aperture receiver with K = 1 decreases from 0.5767 to 0.3868. When the turbulence is weak , the scintillation index decreases from 0.0096 to 0.0070. By increasing the receiving aperture, the scintillation suppression of a single-aperture receiver with 1 aperture is the most obvious. As the number of apertures gradually increases, increasing the area of the receiving aperture has an insignificant effect on the scintillation suppression. At the same time, increasing the number of sub-apertures can significantly reduce the scintillation effect. When D G = 0.1 m and K increases from 1 to 25, under the turbulence condition of , the scintillation index decreases from 0.0096 to 0.0004, under the turbulence condition of G = 1 m and K increases from 1 to 25, under the turbulence condition of It has been reduced from 0.0070 to 0.0004, under the turbulent conditions of it has been reduced from 0.3868 to 0.0213. Increasing the number of sub-apertures has a more obvious aperture averaging effect than increasing the aperture of the receiving aperture. From this, it can be concluded that using the multi-aperture receiving technology can achieve better scintillation suppression effect with a smaller receiving area than that of a single large aperture, and the closest receiving area can be determined according to requirements.

[0064] For the multi-aperture array antenna, the equivalent aperture size is D G is the diameter of the equivalent single large aperture, D is the sub-aperture size, and K is the number of sub-apertures. The aperture averaging effect refers to the phenomenon that the average power of the coupled optical power increases by increasing the area of the receiving aperture. We use the aperture averaging coefficient to characterize the suppression effect of the antenna on turbulence. The smaller the aperture averaging coefficient, the smaller the scintillation index and the stronger the turbulence suppression effect. Increasing the receiving aperture D will increase the average power while introducing more severely distorted optical signals. In practice, the value of D / r0 is usually used to determine the size of the receiving aperture. The larger the receiving aperture D and the stronger the turbulence, the smaller the atmospheric coherence length r0, and the larger this value, the more severely distorted the coupled detected optical signal is. In the multi-aperture receiving scheme, D / r0≈1, and the equivalent aperture averaging coefficient of the multi-aperture receiving is:

[0065]

[0066] It can be seen from the above formula that when the wavelength is constant, the aperture averaging coefficient is only related to the aperture size and the path length. Referring to Figure 7 the total receiving range D in the horizontal link G = 0.4m for the aperture averaging coefficient, it can be seen that the more the number of sub-apertures, the better the turbulence suppression effect of the antenna under different turbulence intensities. However, in an actual receiver, the number of sub-apertures cannot be increased infinitely, and the subsequent complex signal processing module and the introduction of noise will reduce the signal-to-noise ratio of the detector.

[0067] S2. Intelligently adjust the number of optical beam combining sub-apertures in combination with the atmospheric refractive index structure constant, communication link length, signal optical wavelength, and channel correlation coefficient to ensure that the combined optical signals are independent of each other, and perform coupled reception of the optical signals and correction of the first and second order Zernike aberrations based on the closely packed multi-aperture optical antenna that determines the receiving area and the number of sub-apertures.

[0068] Considering the electrical synthesis method, the performance will only get better with the increase in the number of sub-apertures when the sub-apertures are independent. Therefore, the focus of this solution lies in the flexible change of the independent region. Determine the spacing and number of sub-apertures for coherent synthesis, that is, the optical beam combining region, which is related to the atmospheric coherence length r0 determined by the atmospheric refractive index structure constant, the communication link length, and the signal light wavelength. The detailed determination of the coherent synthesis region of the receiving sub-apertures is as follows:

[0069] The calculation formula for the atmospheric coherence length r0 is:

[0070]

[0071] where r0 is the atmospheric coherence length, is the atmospheric refractive index structure constant, L is the communication link length, k is the wave number, k = 2π / λ, λ is the wavelength, which corresponds to the diffraction-limited diameter distorted by atmospheric turbulence. When the telescope aperture is greater than this parameter, the imaging resolution no longer increases with the increase in the receiving aperture.

[0072] In the current design scheme of multi-aperture receiving antennas, if the sub-aperture spacing is greater than the coherence length, they are considered independent. This theory is applicable to medium and weak turbulence cases. In strong turbulence, r0 decreases, while the correlation coefficient between two points at the same distance on the receiving surface increases. When there is a correlation between sub-apertures, the correlation coefficient should be considered. Among them, when the correlation coefficient between two observation points (two sub-apertures) on the receiving plane drops to 1 / e 2 or zero, they can be regarded as two independent points, and this distance is named the correlation width of the light intensity on the receiving surface. The correlation width number p c refers to the minimum spacing at which the light intensity fading between two sub-apertures separated by a certain distance remains independent of each other. The sub-aperture spacing of the multi-aperture receiving array antenna should be greater than the correlation width p at the plane where the laser arrives c to be regarded as independent channels. Therefore, the channel correlation coefficient between two sub-apertures in the closely-packed multi-aperture optical antenna:

[0073]

[0074] where i and j represent two sub-apertures respectively, s ij is the distance between the centers of the two sub-apertures, are the scintillation indices at the i and j sub-apertures respectively, and C ij is the covariance coefficient between the two sub-apertures.

[0075] Based on the covariance of irradiance being a function of the distance s, in a weak turbulence environment, the covariance function of light intensity is:

[0076]

[0077] In a strong turbulence environment, the covariance function of the optical intensity is:

[0078]

[0079] where is the Rytov variance, and L is the communication link length.

[0080] Through the above channel correlation model, the influence of the aperture spacing and the number of apertures on the performance of the multi-aperture receiving antenna can be accurately estimated at all turbulence intensities. By reflecting the turbulence intensity through the Rytov variance, the relationship between ρ c and r0 changing with the turbulence intensity can be obtained. It can be obtained that the coherence width increases with the enhancement of turbulence, and the atmospheric coherence length decreases with the enhancement of turbulence. According to existing experience, the spacing of the sub-apertures should be near the correlation width ρ c and the diameter should be within the scale of the coherence length. For a multi-aperture receiver, it is first necessary to fix the receiver area, which is determined by the aperture diameter, communication link length, turbulence intensity, etc. Then, the aperture interval and the number of sub-apertures are calculated according to the suppression effect of the multi-aperture receiving antenna on turbulence.

[0081] For communication with a fixed link, the more the number of sub-apertures divided in the receiving area, the more obvious the mitigation effect on turbulence after optical synthesis. Considering that in the electrical synthesis method, it is required that the optical signals are independent of each other. In this scheme, taking the center distance of each optical coherent beam combination module as a reference to ensure the independence of electrical synthesis, by changing the size of the optical beam combination area to adapt to different turbulence conditions, and at the same time avoiding energy waste caused by too large sub-aperture spacing.

[0082] S3. The optical signal passes through the optical beam splitter, and a part of the optical signal is input to the coupled energy photodetector to be converted into a voltage or current feedback signal and input to the control module, and the energy of the other part of the optical signal is input to the N×1 adaptive beam synthesis module.

[0083] The optical beam splitter can be selected as a 95:5 or 98:2 optical beam splitter according to requirements. If a 95:5 optical beam splitter is used, 5% of the optical signal is input to the coupled energy photodetector to be converted into a voltage or current feedback signal and then input to the control module, and 95% of the optical signal is input to the N×1 adaptive beam combining module. The coupled energy photodetector uses a photon detector, a photodiode, a phototransistor, an avalanche photodiode, or a photomultiplier tube that converts an optical signal into a voltage or current signal. The coupled optical power of a single aperture should be higher than the sensitivity of the detector, and the operating wavelength range of the photodetector should cover the optical wavelength of the signal laser beam. The control module uses a multi-channel adaptive fiber coupling array controller, which is used to generate an output control voltage by at least using a random gradient descent algorithm, a dithering algorithm, a deep learning algorithm, or a reinforcement learning algorithm. The control voltage acting on the phase modulator is used to achieve adaptive optical coherent synthesis, and the control voltage acting on the receiving coupling array is used to adaptively improve the coupling efficiency of spatial light.

[0084] S4. Based on the intelligently adjusted N×M sub-apertures, the optical signals are coherently combined into one optical signal through the N×1 adaptive beam combining module, and finally M independent optical signals are formed in total.

[0085] The adaptive beam combining module based on phase compensation combines N optical signals into one in a binary tree cascade manner, and a directional coupler with a corresponding splitting ratio is selected for coherent synthesis according to the input light intensity ratio. The N×1 adaptive beam combining module consists of a synthesis phase modulator, a directional coupler, a synthesis photodetector, and a synthesis piston aberration controller, which is used to compensate for the piston aberration between the adaptive fiber coupler arrays. Among them, the phase modulator adjusts the phase of each received sub-signal, and after wavelength-scale phase compensation, it is input to the coupler for coherent synthesis; path selection, according to the change of the correlation width p c on the receiving surface, changes the number of sub-paths for coherent synthesis, controls the path of the signal through an optical switch, connects to the coupler to continue coherent synthesis, or connects to the photodetector to be converted into an electrical signal for digital demodulation; the synthesis piston aberration controller receives the electrical signal of the synthesis coupled energy photodetector and uses an optimal control algorithm to generate an output control voltage.

[0086] S5. Direct detection or coherent detection is performed on the M optical signals, which are converted into M electrical signals, and the M electrical signals are combined and output into one electrical signal through electrical processing, and the electrical signal is judged and demodulated.

[0087] See Figure 3, the arrangement of the adaptive fiber coupler array is triangular, square, hexagonal, circular or annular; at the same time, for the optical combination area distribution of the hexagonal array and the combined model distribution of the square array, the sub-apertures are closely arranged on the receiving end face, and the receiving area can also be increased by stacking array modules.

[0088] See Figure 4 , which shows the overall scheme of the optical synthesis method. In Figure 4 , the correction of the first and second order Zernike aberrations can adopt the single-channel coupled optical signal or the optical power intensity output by the optical synthesis module as the performance index to perform closed-loop control on the corresponding optical signal aperture of the adaptive fiber coupler.

[0089] See Figure 5 , which shows the overall scheme of the electrical synthesis method. In Figure 5 , the optical signal is converted into an electrical signal and electrical synthesis is performed.

[0090] See Figure 6 , which shows the scintillation index at different aperture numbers under different aperture sizes in the vertical link.

[0091] See Figure 7 , which shows the change of the turbulence suppression effect of different sub-aperture numbers under different turbulence intensities in the horizontal link when the diameter of the multi-aperture receiving antenna range is 0.4 m.

[0092] See Figure 8 , when the turbulence is weak, taking 4 sub-aperture regions as an optical coherent beam combination region, outputting a synthesized optical signal, finally forming 16 independent optical signals, converting them into electrical signals, and performing electrical synthesis. In the case of strong turbulence, the coherence width is large, taking 16 sub-apertures as a beam combination region, controlling the optical propagation path through an optical switch, continuing optical coherent beam combination, forming 4 independent optical signals, and then converting them into 4 independent electrical signals and performing electrical synthesis.

[0093] See Figure 9 , where the communication link lengths of the first column, the second column and the third column are 1 km, 3 km and 5 km respectively. In order to verify the beam combination effect of the present invention, the outage probabilities corresponding to the single large aperture, optical and electrical comprehensive synthesis and single electrical synthesis schemes under different channel lengths are compared by simulation. In the simulation, D G=0.4m receiving range as an example, within the same receiving range, the fewer the number of sub-apertures, the larger the diameter of the corresponding single densely packed sub-aperture. When the number of sub-apertures is 1, 4, 16, and 64, the corresponding single sub-aperture sizes are 0.4m, 0.2m, 0.1m, and 0.05m. For the receiving array arrangement with the largest number of sub-apertures, 64 (8x8) units, the N×M optical and electrical integrated synthesis area channel divisions are 1×64, 4×16, 16×4, and 64×1, respectively. The size of represents the turbulence intensity. It is obvious that under different turbulence intensities, the probability of interruption of electrical synthesis is low when the turbulence is weak, and the probability of interruption of photosynthesis is low when the turbulence is strong. The interruption probability of optical and electrical synthesis between strong and weak turbulence is always the lowest.

[0094] See also Figure 9 , we can know the comparison results of different receiving schemes such as optical and electrical comprehensive synthesis, electrical synthesis, and optical synthesis. The present invention can cope with different atmospheric turbulence conditions and improve the stability of communication by intelligently adjusting the number of optical beam combining sub-apertures to avoid energy waste caused by aperture independence. And through multi-aperture reception of optical and electrical comprehensive synthesis, it is possible to use optical coherent beam combining in advance to ensure the independence of the electrical synthesis signal, reduce the complexity of the electrical signal processing part when the aperture array is expanded to a large scale with more units, and increase the light intensity of the single-path detection signal through optical synthesis, so that it can still correctly demodulate the modulated optical signal through the electrical synthesis method under low signal-to-noise ratio conditions.

[0095] It should be noted that, in this article, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the existence of other identical elements in the process, method, article or device including the elements.

[0096] The above are only specific embodiments of the present invention, enabling those skilled in the art to understand or implement the present invention. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to these embodiments shown herein, but rather will be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A method for receiving multi-aperture in space optical communication by comprehensive optical and electrical synthesis, characterized in that, Including: S1. Determine the total receiving area according to the aperture size, communication link length, and turbulence intensity of the closely packed multi-aperture optical antenna; S2. Intelligently adjust the number of optical beam-combining sub-apertures in combination with the atmospheric refractive index structure constant, communication link length, signal light wavelength, and channel correlation coefficient to ensure that the combined optical signals are independent of each other, and perform coupled reception and correction of the first and second-order Zernike aberrations on the optical signals based on the closely packed multi-aperture optical antenna that determines the receiving area and the number of sub-apertures; S3. The optical signal passes through an optical beam splitter, and a part of the optical signal is input to a coupled energy photodetector to be converted into a voltage or current feedback signal and input to a control module, and the energy of the other part of the optical signal is input to an N×1 adaptive beam synthesis module; S4. Based on the intelligently adjusted N×M sub-apertures, the optical signal is coherently combined into one optical signal through the N×1 adaptive beam synthesis module, and finally M independent optical signals are formed in total; S5. Perform direct detection or coherent detection on the M optical signals, convert them into M electrical signals, electrically process and combine the M electrical signals into one electrical signal, and perform decision demodulation on the electrical signal.

2. The multi-aperture receiving method for optical and electrical integrated spatial optical communication according to claim 1, wherein The closely packed multi-aperture optical antenna includes: The closely packed multi-aperture optical antenna uses an adaptive fiber coupler array or an on-chip phased array to achieve the beam splitting and combining functions of the optical path.

3. The multi-aperture receiving method for optical and electrical integrated space optical communication according to claim 1, wherein The intelligent adjustment of the number of optical beam-combining sub-apertures in combination with the atmospheric refractive index structure constant, communication link length, signal light wavelength, and channel correlation coefficient includes: When the correlation coefficient between two sub-apertures is less than 1 / e 2 it can be regarded as an independent channel. The channel correlation coefficient between two points on the receiving plane in the closely-packed multi-aperture optical antenna is as follows: where \(i\) and \(j\) respectively represent two sub-apertures, and \(s\) ij is the distance between the centers of the two sub-apertures, are the scintillation indices at the two sub-apertures \(i\) and \(j\), and \(C\) ij is the covariance coefficient between the two sub-apertures.

4. The multi-aperture receiving method for optical and electrical integrated synthesis of space optical communication according to claim 3, wherein, The intelligent adjustment of the number of optical beam-combining sub-apertures in combination with the atmospheric refractive index structure constant, communication link length, signal light wavelength, and channel correlation coefficient further includes: Based on the covariance of irradiance being a function of the distance s, in a weak turbulence environment, the covariance function of light intensity is: In a strong turbulence environment, the covariance function of light intensity is: where, is the Rytov variance, and L is the communication link length.

5. The multi-aperture receiving method for optical and electrical integrated synthesis in space optical communication according to claim 1, wherein The coupled energy photodetector includes: A photon detector, a photodiode, a phototransistor, an avalanche photodiode, or a photomultiplier tube that realizes the conversion of an optical signal into a voltage or current signal.

6. The multi-aperture receiving method for optical and electrical integrated spatial optical communication according to claim 1, characterized in that, The N×1 adaptive beam synthesis module includes: The N×1 adaptive beam synthesis module is composed of a synthesis phase modulator, a directional coupler, a synthesis photodetector, and a synthesis piston aberration controller, and is used to compensate for the piston aberration between the adaptive fiber coupler arrays.

7. The multi-aperture receiving method for optical and electrical integrated spatial optical communication according to claim 1, wherein The electrical signal synthesis of the M electrical signals includes: Adopt an analog or digital combination method to perform electrical signal synthesis on the M electrical signals.

8. The method for receiving multi-aperture in optical and electrical integrated spatial optical communication according to claim 1, characterized in that The adaptive fiber coupler array includes: The layout of the adaptive fiber coupler array is triangular, square, hexagonal, circular, or annular; and the overall receiving aperture and transmitting aperture can be increased by increasing the number of adaptive fiber couplers.

9. The multi-aperture receiving method for optical and electrical integrated synthesis of space optical communication according to claim 1, characterized in that, The control module includes: A multi-channel adaptive fiber coupler array controller, which is used to generate an output control voltage by using a stochastic gradient descent algorithm, a dithering algorithm, a deep learning algorithm, or a reinforcement learning algorithm.

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