A beaconless space optical communication alignment integrated method based on delta-sigma modulation

Abstract

The application discloses a kind of based on Delta-Sigma modulation's beaconless space optical communication alignment integration method, belong to free space optical communication field, comprising: analog signal is carried out Delta-Sigma modulation to be converted into digital bit stream DSM sequence, it is combined after with communication digital signal, modulated to optical carrier becomes optical carrier signal and is transmitted;Optical carrier signal is reflected after reflecting mirror, is divided into two beams by beam splitter;First light beam successively through four quadrant detection, amplification, analog-digital conversion, low-pass filtering, to restore analog signal, the maximum cross-correlation result obtained by the cross-correlation calculation of analog signal and reference signal of same frequency, as the amplitude of analog signal, to calculate the deviation of the pointing angle of first light beam, and the angle of reflecting mirror is adjusted according to deviation to realize light beam alignment;Second light beam is used to realize communication function.The application can improve the pointing alignment accuracy of space light beam under the premise of not increasing system complexity and cost.

Description

Technical Field

[0001] This invention belongs to the field of free-space optical communication, and more specifically, relates to an integrated alignment method for beaconless spatial optical communication based on Delta-Sigma modulation. Background Technology

[0002] In recent years, free-space optical communication technology has been gradually developing and has been widely applied in various fields worldwide. It possesses the advantages of traditional wireless microwave and fiber optic communication, such as large capacity, unlimited bandwidth, good security, ease of deployment, and flexible networking. However, due to its point-to-point, end-to-end transmission mode, high-precision pointing alignment of the laser beam is a prerequisite and key factor for ensuring the stable establishment of the space optical link. On the other hand, to reduce the complexity and cost of space optical communication terminals, integrating communication lasers into an integrated alignment architecture is considered a feasible solution.

[0003] However, this integrated communication and alignment spatial optical system results in relatively low laser power for alignment, especially in scenarios with high spatial optical link loss. Currently, spatial optical alignment generally employs a direct power detection method based on 4-QD (Four-Quadrant Detector). This method calculates the distance of the light spot from the detector center by comparing the output power of the four quadrant detectors, and then feeds this information back to the front-end mirrors to calibrate the optical path, thus achieving spatial beam alignment. However, this method suffers from significant errors and low accuracy when the received spatial optical power is low, making it particularly difficult to achieve satisfactory results in integrated communication and alignment spatial optical systems.

[0004] Using high-power beacon light to assist alignment inevitably increases the structural complexity and cost of the space optical communication system, which also contradicts the concept of integrated communication and alignment. Therefore, in general, existing space optical alignment methods struggle to achieve a balance between cost and accuracy. Summary of the Invention

[0005] In view of the above-mentioned defects or improvement needs of the existing technology, the present invention provides a beaconless spatial optical communication alignment method based on Delta-Sigma modulation, which aims to improve the spatial beam pointing alignment accuracy at low received optical power while maintaining low complexity and low cost.

[0006] To achieve the above objectives, according to a first aspect of the present invention, a beaconless spatial optical communication alignment integration method based on Delta-Sigma modulation is provided, comprising:

[0007] S1, at the transmitting end, the analog signal is subjected to Delta-Sigma modulation to convert it into a digital bit stream (DSM) sequence. The DSM sequence is then combined with the communication digital signal and modulated onto an optical carrier to become an optical carrier signal for transmission.

[0008] S2, at the receiving end, the optical carrier signal is reflected by a reflector and then split into two beams by a beam splitter. The first beam is sequentially subjected to four-quadrant detection, amplification, analog-to-digital conversion, and low-pass filtering to recover the analog signal from the first beam. The maximum cross-correlation result obtained by cross-correlation calculation between the analog signal and a reference signal of the same frequency is used as the amplitude of the analog signal to calculate the deviation of the pointing angle of the first beam. The angle of the reflector is adjusted according to the deviation to achieve beam alignment. The second beam is used to realize the communication function.

[0009] According to a second aspect of the present invention, a beaconless spatial optical communication alignment integrated device based on Delta-Sigma modulation is provided, comprising a transmitter and a receiver.

[0010] The sending end includes:

[0011] A laser source, used to emit a laser carrier wave;

[0012] Delta-Sigma modulators are used to perform Delta-Sigma modulation on analog signals to convert them into digital bitstream DSM sequences;

[0013] An electro-optic modulator is used to modulate the combined DSM sequence and communication digital signal onto the laser carrier.

[0014] A spatial optical transmission module is used to transmit the optical carrier signal;

[0015] The receiving end includes:

[0016] The optical carrier signal is reflected by the reflector and split into two beams by the beam splitter.

[0017] The four-quadrant detector, the first amplification module, the first ADC module, and the filtering module are used to sequentially perform four-quadrant detection, amplification, analog-to-digital conversion, and low-pass filtering on the first beam to recover the analog signal from the first beam.

[0018] The signal processing module is used to calculate the maximum cross-correlation result obtained by cross-correlation calculation between the analog signal and the reference signal of the same frequency, and use the result as the amplitude of the analog signal to calculate the deviation of the pointing angle of the first beam.

[0019] A control module is used to adjust the angle of the reflector according to the deviation to achieve beam alignment.

[0020] In summary, compared with the prior art, the above-described technical solutions conceived by this invention can achieve the following beneficial effects:

[0021] (1) The beaconless space optical communication alignment integration method based on Delta-Sigma modulation provided by this invention converts the analog feature signal for alignment into a digital bit stream after Delta-Sigma modulation. This bit stream can be easily combined with the communication digital signal in the form of a training sequence or frame header to achieve the integration of communication and alignment functions. No additional beacon optical path is required to assist alignment, which can reduce the complexity and cost of space optical communication terminals.

[0022] (2) The beaconless spatial optical communication alignment method based on Delta-Sigma modulation provided by this invention allows the analog characteristic signal used for alignment to be applied to the cross-correlation algorithm at the receiver. Through correlation operations, it can effectively amplify the SNR in the 4-QD output. Therefore, it can improve the beam pointing angle deviation measurement accuracy under low received optical power conditions, thereby improving the alignment accuracy of the spatial beam through feedback. Compared with the traditional method of using high-power beacon light to improve accuracy, this invention can effectively improve the spatial beam pointing alignment accuracy under weak signal conditions without increasing the complexity of the system terminal structure.

[0023] (3) The beaconless spatial optical communication alignment integrated device based on Delta-Sigma modulation provided by this invention converts the analog feature signal for alignment into a digital signal after Delta-Sigma modulation. Therefore, the generation of the digital feature signal and its combination with the communication digital signal can be implemented by an FPGA, and the signal can be directly output through the I / O port of the FPGA, avoiding expensive DAC devices and further reducing costs. At the same time, the analog feature signal for alignment can be distinguished from the communication data through a simple low-pass filtering operation, without affecting the effect of spatial optical communication; therefore, integrated communication alignment can be achieved without adding an additional beacon optical path to assist alignment, reducing the structural complexity and cost of the system terminal. Attached Figure Description

[0024] Figure 1 A schematic diagram of an integrated alignment device for beaconless spatial optical communication based on Delta-Sigma modulation provided in an embodiment of the present invention;

[0025] Figure 2 A schematic diagram showing the pointing angle measurement error of the cross-correlation scheme and the direct power detection scheme based on Delta-Sigma modulation under different optical powers provided in this embodiment of the invention.

[0026] Figure 3A schematic diagram of the RMSE results of the pointing angle measurement error of the cross-correlation scheme and the direct power detection scheme based on Delta-Sigma modulation under different optical powers provided in the embodiments of the present invention;

[0027] Figure 4 The diagram shows the Delta-Sigma modulator feedback structure and signal modulation schematic provided in this embodiment of the invention. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0029] To improve the pointing accuracy of beaconless free-space optical communication systems under low received optical power conditions, this invention provides an integrated alignment method for beaconless space optical communication based on Delta-Sigma modulation. The overall approach involves converting the analog characteristic signal (i.e., the analog signal) used for alignment into a digital bitstream through Delta-Sigma modulation, combining it with the communication digital signal, and transmitting them together. This achieves integrated communication alignment without adding an additional beacon optical path for alignment assistance, reducing the structural complexity and cost of the system terminal. Furthermore, the analog characteristic signal used for alignment is applied to the cross-correlation algorithm at the receiving end to improve its SNR in the 4-QD output, thereby improving the measurement accuracy of the beam pointing angle deviation under low received optical power conditions, and thus providing feedback to improve the alignment accuracy of the space beam.

[0030] like Figure 1 As shown, this embodiment of the invention provides a beaconless spatial optical communication alignment integration method based on Delta-Sigma modulation, comprising:

[0031] S1, the analog signal is subjected to Delta-Sigma modulation to convert it into a digital bit stream (DSM) sequence. The DSM sequence is then combined with the communication digital signal and modulated onto an optical carrier to become an optical carrier signal for transmission.

[0032] Specifically, at the transmitting end, the analog characteristic signal (i.e., the analog signal) is Delta-Sigma modulated to convert it into a digital bit stream, denoted as a DSM (Delta-Sigma Modulate) sequence; the DSM sequence is then combined with the communication digital signal and output; the new digital signal (i.e., the combined signal) is modulated onto the corresponding optical carrier by an electro-optic modulator, and then transmitted into space using a collimator and a reflector.

[0033] The alignment analog characteristic signal is modulated by a Delta-Sigma modulator and converted into a digital bit stream, which is then combined with the communication digital signal and transmitted together to achieve integrated communication alignment.

[0034] The alignment uses low-frequency analog sine or cosine signals, within the bandwidth of a four-quadrant detector, for example, 0-50MHz. After signal processing, these signals are used to improve the measurement accuracy of beam pointing angle deviation under low received optical power.

[0035] S2, the optical carrier signal is reflected by the reflector and then split into two beams by the beam splitter;

[0036] The first beam is sequentially subjected to four-quadrant detection, amplification, analog-to-digital conversion, and low-pass filtering to recover the analog signal from the first beam. The maximum cross-correlation result obtained by cross-correlation calculation between the analog signal and a reference signal of the same frequency is used as the amplitude of the analog signal. The deviation of the pointing angle of the first beam is calculated, and the angle of the reflector is adjusted according to the deviation to achieve beam alignment. The second beam is used to realize the communication function.

[0037] The maximum cross-correlation result of the beaconless spatial optical communication alignment integration method based on Delta-Sigma modulation is R. i =A i B / 2; where i is the quadrant number, A i B is the amplitude of the analog signal recovered in the i-th quadrant, and B is the amplitude of the reference signal.

[0038] Preferably, the second beam passes through a photodetector, an analog-to-digital converter, and communication-related signal processing in sequence to achieve communication functionality.

[0039] Specifically, such as Figure 1As shown, at the receiving end, after the laser beam is transmitted through the spatial optical link, it is received sequentially by reflectors A and B (the setting of reflector B is not mandatory and can be selected according to the actual optical path design requirements). Then, it is split into two paths by the BS (beamsplitter). One path is used as a collimated laser beam and focused onto the surface of the 4-QD through a lens. The output of the 4-QD is amplified and then acquired by the ADC for signal processing. After obtaining the beam pointing angle deviation through signal processing, the reflector A at the receiving end is controlled through a feedback link to achieve high-precision laser beam alignment. The other beam is coupled into the optical fiber by the collimator, amplified, and then detected by the PD (photodetector) to achieve communication function.

[0040] The alignment uses low-frequency analog sine or cosine signals as analog characteristic signals, which are used in the signal processing algorithm at the receiver to improve the measurement accuracy of beam pointing angle deviation under low received optical power. The signal processing used for alignment at the receiver includes: low-pass filtering, cross-correlation calculation, and pointing angle deviation measurement.

[0041] The process includes: low-pass filtering to recover the analog characteristic signal from the digital bit stream modulated by the Delta-Sigma modulator in the 4-QD output, distinguishing it from the communication digital signal; cross-correlation calculation to perform cross-correlation operation on the recovered analog characteristic signal and a reference signal of the same frequency, thereby amplifying the 4-QD output power under low received optical power conditions, separating it from background noise, and improving its SNR; and beam pointing angle deviation measurement to calculate the beam pointing angle deviation by comparing the output power of each quadrant of the 4-QD after cross-correlation operation, improving the measurement accuracy of beam pointing angle deviation under low power conditions.

[0042] By performing low-pass filtering on the combined signal at the corresponding analog characteristic signal frequency, the Delta-Sigma modulated digital bitstream portion of the 4-QD output can be recovered back to the analog characteristic signal, which can be easily distinguished from the communication digital signal. The recovered analog characteristic signal can also be applied to the cross-correlation algorithm. By performing cross-correlation calculation with a reference signal of the same frequency, the power of the recovered analog characteristic signal can be amplified, enabling it to be separated from background noise under low received optical power conditions, thereby improving the SNR. The calculation method of the entire cross-correlation result Ri is as follows:

[0043]

[0044] S i (t)=Bsin(2πf i t+θ)

[0045]

[0046] Where i represents different quadrants of 4-QD; V i(t) represents the analog characteristic signal output in each quadrant of the 4-QD, and A is its amplitude. For its phase, N i (t) represents the noise it contains; S i (t) is the reference signal used for cross-correlation, B is its amplitude, and θ is its phase; f i The frequencies of the analog characteristic signal and the reference signal are used; T represents the length of the data for cross-correlation; from R... i It is not difficult to find in the calculation process that when the data length T used for cross-correlation is long enough, R i The second term in the result is close to 0. The third term, noise N i (t) is not correlated with the reference signal used for cross-correlation, so this term is also close to 0; therefore, the final cross-correlation result R is obtained. i Approximate to:

[0047]

[0048] Controlling the phase θ of the reference signal used for cross-correlation with the phase of the analog characteristic signal Consistency, that is This will allow us to obtain the maximum cross-correlation result R. i =AB / 2, using the amplitude B of the reference signal to amplify the output of the analog characteristic signal (i.e., using the maximum cross-correlation result R). i =AB / 2 is used as the amplitude of the recovered analog characteristic signal, replacing its original amplitude A, and participates in the subsequent calculation of the beam pointing angle deviation, thereby improving its SNR;

[0049] Pointer angle deviation measurement is achieved by comparing the amplified analog characteristic signals after cross-correlation calculations in each quadrant, and outputting the result R. i =AB / 2 is used to calculate the deviation of the beam pointing angle, thereby improving the measurement accuracy of the beam pointing angle deviation under low received optical power conditions.

[0050] It is understandable that each quadrant in the four quadrants has a maximum cross-correlation result. Based on the maximum cross-correlation results of the four quadrants, the bias is calculated. The bias calculation formula is:

[0051]

[0052] Where Δx and Δy are the deviations between the beam center and the center of the four-quadrant detector, corresponding to the deviations in the beam pointing angle; I A,B,C,D This corresponds to the output power in different quadrants of different four-quadrant detectors, which also corresponds to the received optical power in different quadrants. However, due to the presence of environmental background noise I... back And the dark current I of 4QD itselfdark These effects will cause errors in the calculated Δx and Δy, as shown in the following formula:

[0053]

[0054] Among them I QD =I A +I B +I C +I D The sum of the output power in the four quadrants, when I QD When the relative size is large (i.e., the received optical power is high enough), the ambient background noise I back And the dark current I of 4QD itself dark The impact on the calculation results of Δx and Δy is very small; however, when I QD When the relative optical power is low (i.e., the received optical power is low), the ambient background noise I back And the dark current I of 4QD itself dark The impact on the calculation results of Δx and Δy cannot be ignored.

[0055] Introducing analog characteristic signals for cross-correlation calculation, and then amplifying the cross-correlation result R... i To replace the power directly output by the 4QD (i.e., using R) i Replace the original amplitude of the analog signal, and change R. i By using the amplitude of the analog signal in the deviation calculation, the influence of background noise and dark current can be reduced as much as possible under low received optical power, thereby improving the measurement accuracy of the pointing angle deviation.

[0056] It is understandable that when the analog characteristic signal is a low-frequency cosine signal, its maximum cross-correlation result is also Ri = AB / 2.

[0057] like Figure 2 As shown, this embodiment also compares the theoretical offset pointing angle measurement errors of the cross-correlation scheme based on Delta-Sigma modulation and the direct power detection scheme under different optical powers; where the horizontal axis represents the actual offset of the simulated laser spot position in the X-axis direction of the 4-QD surface, and the vertical axis represents the spot offset angle (corresponding to the magnitude of the position offset) calculated by the processing algorithm; from Figure 2 The results show the differences between different schemes and the theoretical curves; under lower received optical power conditions, the cross-correlation scheme based on Delta-Sigma modulation yields results closer to the theoretical curve; while under different received optical power conditions, the corresponding RMSE results are as follows: Figure 3 As shown in Table 1, the specific values ​​are as follows.

[0058] Table 1

[0059]

[0060] According to Table 1 and Figure 3 The results show that when the received optical power is relatively high (>-30dBm), the errors in the pointing angle deviation measured by both schemes are not large, and it can be considered that the alignment of the space beam can be achieved well. However, when the optical power is further reduced (<-30dBm), the error of the direct power detection scheme increases rapidly, and the RMSE value of the deviation angle error reaches 67.61μrad when the received optical power is -40dBm. In contrast, the Delta-Sigma-based cross-correlation scheme can still maintain an RMSE value of 35.24μrad for the deviation angle error when the received optical power is -45dBm. Under the condition of lower received optical power, the measurement accuracy of the pointing angle deviation is significantly improved, thereby improving the alignment accuracy of the space beam.

[0061] It should be noted that the above description is merely exemplary and should not be construed as the sole limitation of the present invention. In other embodiments of the present invention, due to differences in the 4-QD devices used or other losses in the link, the relationship between the incident light power and the calculated pointing angle deviation measurement result may change accordingly, but the overall trend compared with the direct power detection scheme is consistent with this embodiment.

[0062] This invention provides a beaconless spatial optical communication alignment integrated device based on Delta-Sigma modulation, including a transmitter and a receiver;

[0063] The sending end includes:

[0064] A laser source, used to emit a laser carrier wave;

[0065] Delta-Sigma modulators are used to perform Delta-Sigma modulation on analog signals to convert them into digital bitstream DSM sequences;

[0066] An electro-optic modulator is used to modulate the combined DSM sequence and communication digital signal onto the laser carrier.

[0067] A spatial optical transmission module is used to transmit the optical carrier signal.

[0068] Specifically, the transmitting end includes: a laser source, a Delta-Sigma modulator, a digital signal output module, and an electro-optic modulator; the laser source is used to transmit a laser carrier of the corresponding wavelength; the Delta-Sigma modulator performs Delta-Sigma modulation on the alignment analog characteristic signal, converting it into a digital bit stream, denoted as the DSM training sequence; the DSM training sequence is combined with the communication digital signal and output; it is connected to the input of the electro-optic modulator through the digital signal output module; the electro-optic modulator is used to modulate the digital signal onto the laser carrier of the corresponding wavelength for transmission.

[0069] The receiving end includes:

[0070] The optical carrier signal is reflected by the reflector and split into two beams by the beam splitter.

[0071] The four-quadrant detector, the first amplification module, the first ADC module, and the filtering module are used to sequentially perform four-quadrant detection, amplification, analog-to-digital conversion, and low-pass filtering on the first beam to recover the analog signal from the first beam.

[0072] The signal processing module is used to calculate the maximum cross-correlation result obtained by cross-correlation calculation between the analog signal and a reference signal of the same frequency, and use the result as the amplitude of the analog signal to calculate the deviation of the pointing angle of the first beam.

[0073] Specifically, the collimation module at the receiver includes a 4-QD, a first amplification module, a first ADC module, a signal processing module, and a feedback link. The 4-QD detects the center spot position of the laser beam and outputs the received optical power in the corresponding quadrant. The first amplification module amplifies the output power of the 4-QD. The first ADC samples the output of the amplification module and sends it to the signal processing module. The signal processing module calculates the pointing angle deviation of the laser beam using an algorithm, and then uses the feedback link to control the reflector (i.e., reflector B) at the system receiver, thereby controlling the alignment of the spatial beam. Reflector B is used to adjust the pointing angle of the received spatial beam to adjust the collimation of the spatial beam. The beam splitter (i.e., beam splitter mirror) is located after the reflector and is used to split the received spatial laser into two beams, one for collimation and the other for communication.

[0074] Among them, the alignment analog characteristic signal is a low-frequency analog sine signal, which is also used in the signal processing module of the collimation module at the receiving end to improve the measurement accuracy of the beam pointing angle deviation under low received optical power; the signal processing module is used to perform the following in sequence: low-pass filtering, cross-correlation calculation, and pointing angle deviation measurement.

[0075] By low-pass filtering at the frequency corresponding to the analog characteristic signal, the digital bitstream portion modulated by the Delta-Sigma modulator in the 4-QD output can be recovered back to the analog characteristic signal, which can be easily distinguished from the communication digital signal. The recovered analog characteristic signal can be applied to the cross-correlation algorithm. By performing correlation calculations with a reference signal of the same frequency, its output power in the 4-QD can be amplified, enabling it to be separated from background noise under low received optical power conditions and improving SNR. The beam pointing angle deviation measurement calculates the deviation of the beam pointing angle by comparing the amplified high SNR results of cross-correlation operations in each quadrant, thereby improving the measurement accuracy of the beam pointing angle deviation under low received optical power conditions.

[0076] A control module is used to adjust the angle of the reflector according to the deviation to achieve beam alignment.

[0077] Preferably, the device further includes: a second amplification module, a photoelectric detection module, a second ADC module, and a communication-related signal processing module, used to sequentially amplify, photoelectricly detect, convert analog to digital, and process communication-related signals to achieve communication functions.

[0078] Specifically, the device further includes a receiver communication module, which includes a second amplification module, a PD, a second ADC module, and a signal processing module; the second amplification module is used to amplify the laser signal coupled into the optical fiber; the PD is used to receive the optical signal and convert it into an electrical signal; the second ADC module is used to sample the output of the amplification module and send it to the signal processing module for communication-related signal processing to realize the corresponding communication function.

[0079] Furthermore, the device also includes a spatial optical transmission module, which comprises: a collimator, a spatial optical link, a reflector A, and a beam splitter; the collimator is used to emit laser light from the optical fiber into space, or to couple spatial laser light into the optical fiber; the spatial optical link serves as the medium for laser transmission. The reflector A is used to adjust the direction of the optical path and can be designed according to actual needs.

[0080] Preferably, the device further includes an FPGA for combining DSM training sequences and communication digital signals, and transmitting them through the I / O ports of the FPGA.

[0081] Specifically, in order to further reduce the implementation cost of the device, as an optional implementation method, in this embodiment, the generation and combination of DSM training sequences and communication digital signals are both completed by FPGA, and the digital signal output module is an external I / O port of FPGA, thereby avoiding the use of expensive DAC devices and further reducing the structural complexity and cost of the device.

[0082] Furthermore, the specific process by which the Delta-Sigma modulator converts analog signals into digital signals is as follows: Figure 4 As shown, the process includes three parts: oversampling, noise shaping, and quantization. First, the original analog signal is oversampled to expand its Nyquist region, resulting in a more uniform distribution of quantization noise over a wider frequency range. Then, the level value of each sample is processed by the feedback structure of the Delta-Sigma modulator, pushing the quantization noise out of the signal band, thus reducing residual noise and achieving noise shaping. Finally, in the case of 1-bit quantization, the output is a 1-bit data stream, converting the analog signal into a digital signal in this way. In this embodiment, the feedback structure of the Delta-Sigma modulator is as follows: Figure 4 As shown, its transfer function (NTF) in the z-domain is expressed as follows:

[0083]

[0084] Wherein, a1~a4 and g1~g4 are the coefficients of each node in the feedback structure, and a1=0.557, a2=0.244, a3=0.049, a4=0.005, g1=-0.001, g2=-0.007. Optionally, the parameter combination used in this embodiment corresponds to a low frequency point of 10-MHz, and the sampling rate is 100 times the Nyquist sampling rate.

[0085] It should be noted that the above description is merely exemplary and should not be construed as the sole limitation of the present invention. In other embodiments of the present invention, the corresponding analog signal frequency and oversampling rate can be adjusted by changing the coefficients in the feedback structure of the Delta-Sigma modulator. Similar results can be achieved in the aforementioned integrated spatial optical communication alignment device.

[0086] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A beaconless spatial optical communication alignment integration method based on Delta-Sigma modulation, characterized in that, include: S1, at the transmitting end, the analog signal is subjected to Delta-Sigma modulation to convert it into a digital bit stream (DSM) sequence. The DSM sequence is then combined with the communication digital signal and modulated onto an optical carrier to become an optical carrier signal for transmission. S2, at the receiving end, the optical carrier signal is reflected by a reflector and split into two beams by a beam splitter; the first beam is sequentially subjected to four-quadrant detection, amplification, analog-to-digital conversion, and low-pass filtering to recover the analog signal from the first beam. The maximum cross-correlation result obtained by cross-correlation calculation between the analog signal and a reference signal of the same frequency is used as the amplitude of the analog signal to calculate the deviation of the pointing angle of the first beam, and the angle of the reflector is adjusted according to the deviation to achieve beam alignment; the second beam is used to realize the communication function.

2. The method as described in claim 1, characterized in that, The analog signal is a low-frequency sine or cosine signal, with a frequency range within the bandwidth of the four-quadrant detector.

3. The method as described in claim 2, characterized in that, The maximum cross-correlation result is R i = A i B / 2; where, i Quadrant number, A i For the first i The amplitude of the analog signal recovered in the quadrant. B The amplitude of the reference signal.

4. The method as described in claim 1, characterized in that, The second beam passes sequentially through a photodetector, analog-to-digital converter, and communication-related signal processing to achieve communication functionality.

5. A beaconless spatial optical communication alignment integrated device based on Delta-Sigma modulation, characterized in that, Includes the sending end and the receiving end; The sending end includes: A laser source, used to emit a laser carrier wave; Delta-Sigma modulators are used to perform Delta-Sigma modulation on analog signals to convert them into digital bitstream DSM sequences; An electro-optic modulator is used to modulate the combined DSM sequence and communication digital signal onto the laser carrier to form an optical carrier signal; A spatial optical transmission module is used to transmit the optical carrier signal; The receiving end includes: The optical carrier signal is reflected by the reflector and split into two beams by the beam splitter. The four-quadrant detector, the first amplification module, the first ADC module, and the filtering module are used to sequentially perform four-quadrant detection, amplification, analog-to-digital conversion, and low-pass filtering on the first beam to recover the analog signal from the first beam. The signal processing module is used to calculate the maximum cross-correlation result obtained by cross-correlation calculation between the analog signal and the reference signal of the same frequency, and use the result as the amplitude of the analog signal to calculate the deviation of the pointing angle of the first beam. A control module is used to adjust the angle of the reflector according to the deviation to achieve beam alignment.

6. The apparatus as claimed in claim 5, characterized in that, Also includes: The second amplification module, photoelectric detection module, second ADC module, and communication-related signal processing module are used to sequentially amplify, photoelectricly detect, convert analog to digital, and process communication-related signals to achieve communication functionality.

7. The apparatus as claimed in claim 5, characterized in that, Also includes: An FPGA is used to combine DSM training sequences and communication digital signals, and transmit them through the I / O ports attached to the FPGA.

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