Method for online optimization of coaxiality of laser communication terminal transceiver, laser communication terminal and system

Abstract

The application discloses a laser communication terminal transceiving coaxiality online optimization method, comprising the following steps: receiving an optical signal carrying modulation frequency information transmitted by a peer laser communication terminal; calculating the modulation frequency information from the optical signal; the modulation frequency information is determined by the peer laser communication terminal according to the change trend of a received performance index used to reflect the optical signal receiving efficiency of the peer laser communication terminal; and adjusting the scanning direction of a leading aiming mechanism of the local laser communication terminal according to the calculated modulation frequency information, so as to realize online optimization of the transceiving coaxiality of the local laser communication terminal. Further, the corresponding laser communication terminal and system are disclosed. The application can realize online and automatic testing and optimization of the transceiving coaxiality of the laser communication terminal in the case of no beacon light.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of laser communication, and particularly relates to a laser communication terminal transceiving coaxiality online optimization method, a laser communication terminal and a system. BACKGROUND

[0002] Currently, the test and optimization of the transceiving coaxiality of the laser communication terminal mainly includes offline and online modes. Offline measurement and optimization refers to measuring the transceiving coaxiality on the ground through high-precision collimators and other measuring devices, and adjusting the transceiving coaxiality to the optimal state. Offline measurement and optimization of the transceiving coaxiality of the laser communication terminal is mainly based on high-precision measuring instruments and devices, such as three-coordinate measuring instruments, laser collimators, etc., to measure the coaxiality of the laser communication terminal, and adjust the working angle of the pre-acquisition sight to make the transceiving coaxiality of the laser communication terminal reach the optimal state. For example, the patent application with the publication number CN111736358A and the name of “laser communication terminal transceiving coaxial real-time calibration method”. However, the working environment of the laser communication terminal is in space, and the laser communication terminal will experience the vibration of the carrier rocket during the transmission process, which may cause slight deformation or movement of the internal optical path mechanical structure. At the same time, the temperature, humidity, gravity, etc. in space are different from the ground test state, so there is a certain difference between the optimal coaxiality of the laser communication terminal obtained by offline test on the ground and the optimal coaxiality in the space environment, and it is impossible to ensure that the ground test result and the coaxiality in the space remain consistent, and manual optimization can only be performed in space again.

[0003] Currently, the online optimization of the transceiving coaxiality of the laser communication terminal is mainly realized through beacon light. When measuring and adjusting the transceiving coaxiality online, the design is based on the optical path model, the difference between the reflection of the beacon light and the landing point of the optical signal on the calibration guide mirror is converted into the included angle of the transceiving optical axis, so as to realize the online measurement and adjustment of the transceiving coaxiality. For example, the patent application with the publication number CN113630183A and the name of “multi-optical path optical axis automatic coaxial laser communication ground terminal and coaxial control method”. The laser communication terminal transmits beacon light, the difference between the landing point of the reflected light of the beacon light on the calibration guide mirror and the landing point of the optical signal transmitted by the communication terminal on the calibration guide mirror calculates the deflection angle of the optical path, and further adjusts the transmission optical path sighting mirror, so as to realize the online optimization of the transceiving coaxiality of the laser communication terminal. However, this scheme relies on the measurement optical path of the beacon light, the calibration guide mirror, etc., and the addition of these measurement optical paths makes the product structure more complex and the failure rate increases. Moreover, the process of calculating the included angle of the transceiving optical axis relies on the model, and the inaccuracy of the model and the change of the model will affect the calculation result of the included angle of the transceiving optical axis, so as to cause the transceiving coaxiality to be unable to reach the optimal state and the transceiving efficiency to be unable to reach the highest.

[0004] In summary, the off-line transmission-reception coaxiality test cannot be optimized after calibration, and the calibration result is inconsistent with the actual working result; the on-line test and optimization need to use beacon light, and the beacon light emission and calibration guide mirror increase the complexity of the optical path, increase the production and debugging cost, and reduce the product stability. Therefore, there is an urgent need for an on-line automatic laser communication terminal transmission-reception coaxiality optimization method without beacon light. SUMMARY

[0005] To solve the above problems, the application provides a laser communication terminal transmission-reception coaxiality online optimization method, a laser communication terminal and a system, which can perform online and automatic transmission-reception coaxiality optimization without beacon light, thereby improving the optical signal receiving efficiency of the laser communication terminal.

[0006] The technical scheme of the application includes the following aspects:

[0007] The first aspect of the application discloses a laser communication terminal transmission-reception coaxiality online optimization method, comprising the following steps: receiving an optical signal carrying modulation frequency information transmitted by a peer laser communication terminal; calculating the modulation frequency information from the optical signal; the modulation frequency information is determined by the peer laser communication terminal according to the change trend of the reception performance index used to reflect the optical signal receiving efficiency of the peer laser communication terminal; adjusting the scanning direction of the lead aiming mechanism of the local laser communication terminal according to the calculated modulation frequency information, so as to realize the online optimization of the transmission-reception coaxiality of the local laser communication terminal. Through this method, the receiving efficiency of the peer laser communication terminal can be improved.

[0008] Optionally, the method further comprises the following steps: obtaining a reception performance index used to reflect the optical signal receiving efficiency of the local laser communication terminal; determining a modulation frequency according to the change trend of the reception performance index; controlling the lead aiming mechanism of the local laser communication terminal to perform periodic motion at the modulation frequency, so as to transmit an optical signal carrying modulation frequency information to the peer laser communication terminal; the modulation frequency information is used to indicate the scanning direction of the lead aiming mechanism of the peer laser communication terminal, so as to realize the online optimization of the transmission-reception coaxiality of the peer laser communication terminal. In this way, the synchronous online optimization of the transmission-reception coaxiality of the peer laser communication terminal can be realized, thereby improving the receiving efficiency of the local laser communication terminal.

[0009] Optionally, the periodic motion is sinusoidal or cosine motion.

[0010] Optionally, the periodic motion is centered on the offline calibrated transmission-reception coaxial point.

[0011] Optionally, the modulation frequency information in the light signal transmitted by the laser communication terminal comprises a first frequency or a second frequency; wherein the first frequency is used to instruct the laser communication terminal to maintain the current scanning direction movement by controlling the lead aiming mechanism, and the second frequency is used to instruct the laser communication terminal to move in the opposite direction of the current scanning direction by controlling the lead aiming mechanism.

[0012] Optionally, the reception performance index comprises at least one of the spot average energy and the optical power input PA value; the spot average energy is obtained by the follow-up camera of the laser communication terminal; and the optical power input PA value is defined as the PA value obtained by the light signal processor after the light signal coupled to the receiving optical fiber of the laser communication terminal.

[0013] Optionally, the lead aiming mechanism of the laser communication terminal has two orthogonal movement axes; one of the two movement axes is used to perform periodic movement for realizing the modulation function, and the other movement axis is used to realize the scanning function, and the functions realized by the two movement axes are switched when a preset condition is met.

[0014] Optionally, the preset condition is that the change trend of the reception performance index is changed from enhancement to weakening.

[0015] Optionally, the modulation frequency information is calculated from the light signal by using a fast Fourier transform (FFT) algorithm.

[0016] Optionally, the method further comprises: when the reception performance index reaches a preset target, stopping the transmission-reception coaxial degree optimization, and recording the control instruction value of the lead aiming mechanism as an updated transmission-reception coaxial point.

[0017] The second aspect of the present application discloses a laser communication terminal transmission-reception coaxial degree online optimization method, which comprises the following steps: obtaining a reception performance index used to reflect the light signal reception efficiency of the laser communication terminal; determining a modulation frequency according to the change trend of the reception performance index; controlling the lead aiming mechanism of the laser communication terminal to perform periodic movement at the modulation frequency, so as to transmit a light signal carrying the modulation frequency information to the opposite laser communication terminal; and the modulation frequency information is used to instruct the opposite laser communication terminal to adjust the scanning direction of the lead aiming mechanism, so as to realize the online optimization of the transmission-reception coaxial degree of the opposite laser communication terminal. Thus, the reception efficiency of the laser communication terminal can be optimized.

[0018] The third aspect of the present application discloses a laser communication terminal, which comprises a light source generator, a transmitting optical fiber, a receiving optical fiber, an optical signal processor, a coarse servo mechanism, a pre-aiming mechanism, a fine tracking mechanism, a tracking camera and a controller; the pre-aiming mechanism has two orthogonal motion axes, one of which is used to perform a periodic motion for realizing a modulation function, and the other of which is used to perform a scanning function; the controller is electrically connected with the tracking camera, the optical signal processor, the coarse servo mechanism, the pre-aiming mechanism and the fine tracking mechanism respectively, and is used to perform the laser communication terminal transceiver coaxiality online optimization method in any one of the first aspect and the optional items thereof or the second aspect of the present application.

[0019] Optionally, the pre-aiming mechanism and the fine tracking mechanism are both configured with a galvanometer and a driving component thereof.

[0020] The fourth aspect of the present application discloses a laser communication system, which comprises at least two laser communication terminals; the laser communication terminal is the laser communication terminal in the third aspect of the present application and the optional items thereof.

[0021] The present application is applied to the field of laser communication, and can optimize the transceiver coaxiality of two laser communication terminals online, so that the transceiver efficiency of the two laser communication terminals meets the demand of communication.

[0022] The main beneficial effects of the present application are as follows:

[0023] (1) The present application realizes a fundamental breakthrough of the laser communication terminal transceiver coaxiality optimization technology, and for the first time realizes the self-determination, online and real-time collaborative optimization of both ends without relying on beacon light, introducing additional optical path and demanding precise optical model, thereby greatly improving the communication efficiency. The present application converts the optimization process into an intelligent interaction process between the two communication parties, and fundamentally solves the long-term technical bottleneck of the mismatch of the traditional offline calibration environment, the complex structure of the online scheme and the poor stability.

[0024] (2) The present application uses the inherent pre-aiming mechanism of the laser communication terminal to perform high-frequency and small-amplitude periodic motion (such as sinusoidal motion) as a modulation source, and uses the inherent optical signal of the communication link itself as an information carrier, which replaces the independent beacon light emitting link and calibration guide mirror and other optical modules required by the traditional online calibration, greatly simplifies the terminal structure, fundamentally avoids the problems of installation and adjustment errors, potential fault points and performance degradation risks caused by introducing additional optical paths, and significantly improves the stability and reliability of the terminal in complex space environment for long-term work.

[0025] (3) Unlike the traditional scheme relying on accurate optical path modeling to calculate the optical axis angle, the application proposes a collaborative optimization mechanism based on "modulation-solution" to understand the coaxiality state information through the reception performance index reflecting the reception efficiency of the reaction light signal in the signal modulation and solution process of the laser communication terminal at the local and the opposite end, and encode the trend of the change into the modulation frequency of the super-sight, and then the opposite end deciphers it through fast Fourier transform (FFT) algorithm to form a closed-loop control instruction. This method is not sensitive to the accuracy of the system optical model, can adaptively compensate for the optical path drift caused by mechanical stress, temperature change and other factors, has better environmental adaptability and stronger robustness.

[0026] (4) The application can effectively convert the complex coaxiality optimization process into a fully automatic software process. When the satellite is in orbit, only a small amount of key parameters need to be input and the execution instruction is triggered to start the execution in the on-orbit window period, and the real-time and collaborative online optimization of the double end is completed autonomously in the non-window period, which greatly improves the utilization efficiency of the on-orbit communication window and releases the ground measurement and control resources.

[0027] (5) According to the measured data, the application can realize an optimization amplitude of more than 3dB on the PA value of the receiving optical path, which is equivalent to doubling the received optical power. This significant performance improvement has great significance and engineering application value for improving the link margin, improving the communication rate and stability, etc. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 It is a schematic diagram of the application scene of the laser communication terminal.

[0029] Figure 2 It is a schematic diagram of the circuit and optical path structure of the laser communication terminal.

[0030] Figure 3 It is a sine motion curve diagram of the optical axis of the A terminal.

[0031] Figure 4 It is a curve diagram of the average energy change of the light spot detected by the tracking camera of the B terminal.

[0032] Figure 5 It is a schematic diagram of the modulation frequency information of the FFT solution.

[0033] Figure 6 It is a schematic diagram of the coaxiality optimization process of the laser communication terminal transceiver.

[0034] Figure 7 It is a schematic diagram of the software implementation process of the coaxiality optimization of the laser communication terminal transceiver. DETAILED DESCRIPTION

[0035] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative effort belong to the protection scope of the present application.

[0036] A laser communication terminal (LCT) is a carrier of a laser communication transmission link, has advantages of low power consumption, good confidentiality, high transmission rate, strong anti-interference capability, and small terminal volume, and is an effective means to solve high-rate transmission. In the process of mutual communication of the two terminals, the A terminal transmits an optical signal while receiving an optical signal transmitted by the B terminal; the B terminal transmits an optical signal while receiving an optical signal transmitted by the A terminal, as shown in Figure 1

[0037] Currently, the laser communication terminal mainly adopts a cooperative working mode of a coarse servo mechanism and a fine servo mechanism. The coarse servo mechanism has characteristics of a large movement range, a relatively low movement speed, and a relatively low control precision, and is responsible for a wide-range pointing and scanning function of the communication terminal; the fine servo mechanism has characteristics of a small movement range (in the order of milliradians), a high movement speed, and a very high control precision, and is responsible for compensating for the deficiencies (such as a low movement speed and a low control precision) of the coarse servo mechanism. The coarse servo mechanism mainly consists of a rotating motor and a shaft system (referred to as a “support shaft system”) supporting rotation; the fine servo mechanism mainly includes a pre-alignment mechanism (referred to as “pre-alignment”) and a fine tracking mechanism (referred to as “fine alignment”), both of which are composed of a galvanometer and its driving components (such as a piezoelectric driver and a voice coil motor). The coarse servo mechanism and the fine servo mechanism work together to form a servo mechanism of the laser communication terminal.

[0038] The laser communication terminal has various optimization schemes for transceiving coaxiality, and various schemes rely on different optical principles and optical path models. The present application builds a two-way closed-loop cooperative optimization mechanism, does not rely on an optical path model, and can realize online transceiving coaxiality optimization of both terminals by using a pre-alignment mechanism and a tracking camera, without introducing redundant devices and having a low requirement for the complexity of an optical path, and is more adaptable than a scheme based on an optical path model, and fundamentally realizes online optimization of both terminals under a beacon-free light condition.

[0039] ​In the cooperative process, each end of the communication party synchronously plays a dual role, that is, on the one hand, as an information sender, the modulation frequency is determined based on the light signal receiving efficiency of the end itself and is loaded on the communication light signal; on the other hand, as an execution party, the modulation frequency sent by the opposite end is solved in real time and the scanning direction of the end itself is adjusted through a leading aiming mechanism. Through the cross guidance and mutual optimization working logic, it is ensured that the two ends can complete the coaxiality optimization of receiving and transmitting on line, autonomously and synchronously in the actual working environment, and completely get rid of the dependence on the beacon light and artificial intervention.

[0040] Embodiment 1 of the present application provides a beacon-free laser communication terminal (referred to as a laser communication terminal or a terminal for short), mainly comprising an optical machine main body composed of a coarse servo mechanism 7, a fine servo mechanism and a follow-up aiming camera 8 and the like functional units, a light source generator 1, a controller 9, a light signal processor 2 and the like circuit elements realizing electric control and signal analysis functions, and a transmitting optical fiber 3, a receiving optical fiber 4 and the like optical elements, wherein the fine servo mechanism comprises two parts of super aiming and fine aiming.

[0041] As shown in Figure 2 The input end of the optical machine main body is connected to the light source generator 1 through the transmitting optical fiber 3, the output end is connected to the light signal processor 2 through the receiving optical fiber 4, and the coarse servo mechanism contained therein transmits or receives light signals to or from other laser communication terminals.

[0042] Among them, the super aiming galvanometer 5 and the fine aiming galvanometer 6 are the core components in the fine servo mechanism, mainly used for reflecting laser and accurately controlling the reflection direction of laser.

[0043] Among them, the coarse servo mechanism 7 is mainly responsible for large-scale pointing and scanning functions, realizing large-scale movement of the transmitted light and receiving light in a large range.

[0044] Among them, the follow-up aiming camera 8 (referred to as the camera for short) is mainly used for imaging the light signal and outputting the coordinates of the light spot centroid in the camera. Specifically, the follow-up aiming camera detects the position of the light spot and feeds back the electrical signal for reflecting the light spot centroid position information to the controller. The controller calculates the position deviation of the light spot centroid position (i.e. the position of the light spot on the target surface of the camera) relative to the expected position (usually the center of the target surface) based on the feedback signal sent by the camera and converts it into the angle deviation of the incident light, providing the basis for the servo control of super aiming and fine aiming.

[0045] Among them, the controller 9 is electrically connected with the follow-up aiming camera 8, the light signal processor 2, the rotating motor of the coarse servo mechanism 7, and the driving components of the fine servo mechanism (super aiming and fine aiming), respectively, receives the feedback signal sent by the follow-up aiming camera 8 and the PA input value measured by the light signal processor 2, and generates instructions for controlling the motion angle of super aiming and fine aiming based on these feedback information, drives the cooperative action of the coarse and fine two-stage servo mechanisms, and eliminates the above position deviation together to form a closed-loop control.

[0046] It can be understood that the closed-loop control is the most commonly used control mode in servo control. The closed-loop control system mainly consists of a controller 9, an actuator and a sensor. Among them, the coarse servo mechanism 7 and the fine servo mechanism (fine pointing, super pointing) are the actuators in the closed-loop feedback control system of the laser communication terminal; the tracking camera 8 acts as a sensor. The controller 9 is electrically connected with the tracking camera 8, the rotating motor of the coarse servo mechanism 7 and the driving part of the fine servo mechanism, receives the electrical signal fed back by the tracking camera 8, and controls the motion angle of the super pointing and the fine pointing, i.e. the two-dimensional motion angle of the galvanometer in the super pointing and the fine pointing, based on the electrical signal, so as to realize the compound axis control strategy.

[0047] Among them, the optical signal processor 2 is mainly used to realize laser communication. On the one hand, it calculates the power of the input optical signal in the receiving optical fiber 4, i.e. the PA input value, which can be used to measure the receiving efficiency of the terminal; on the other hand, when the PA input value is greater than the communication sensitivity threshold, the optical signal is demodulated and analyzed to realize stable laser communication.

[0048] Further combining Figure 2 As shown, the light source generator 1 generates laser of target wavelength, the generated laser is incident from the transmitting optical fiber 3 of the laser communication terminal, first passes through the super pointing galvanometer 5 and the fine pointing galvanometer 6 in the fine servo mechanism for high frequency fine adjustment, then passes through the coarse servo mechanism 7 for large range pointing (i.e. coarse pointing), and then is emitted from the coarse servo mechanism to the universe space, which is the transmitting light path. The direction of the transmitting light emission is related to the motion angle of the fine servo mechanism (including the motion angle of the fine pointing and the motion angle of the super pointing) and the motion angle of the coarse servo mechanism.

[0049] The laser in the universe space, i.e. the laser transmitted by other laser communication terminals, is first coarsely pointed by the coarse servo mechanism 7, then stably and finely adjusted by the fine pointing galvanometer 6 of the fine servo mechanism, and finally coupled into the receiving optical fiber 4 of the laser communication terminal, which is the receiving light path. The receiving optical fiber 4 sends the received optical signal to the optical signal processor 2 for analysis and processing. Among them, the intensity of the light coupled into the receiving optical fiber 4 (i.e. the receiving efficiency) is related to the direction of the receiving light path, and the direction of the receiving light path is related to the motion angle of the fine servo mechanism (only the motion angle of the fine pointing) and the motion angle of the coarse servo mechanism. When the motion angle of the coarse servo mechanism is fixed, the direction of the receiving light axis is only related to the motion angle of the fine pointing, therefore, the motion angle of the fine pointing determines the spot position in the tracking camera and the direction of the receiving light path.

[0050] It can be understood that the transceiving coaxiality represents the deviation degree of the transmitting optical axis and the receiving optical axis of the laser communication terminal in the spatial direction, i.e. is used for measuring the optical axis consistency of the transmitting optical path and the receiving optical path in the laser communication terminal. The laser communication terminal transmits an optical signal at the same time as receiving an optical signal transmitted by another laser communication terminal. When the transmitting optical path and the receiving optical path of the laser communication terminal are coaxial, i.e. completely coincide, the transceiving efficiency of the two communicating laser communication terminals is the highest.

[0051] In the calibration process, the coarse servo mechanism is usually fixedly aligned to a far-field target, so the receiving optical axis is stabilized and aligned to the target by fine pointing closed-loop control, and the optical axis direction is locked. The final direction of the transmitting optical axis is determined by the beam deflection angle determined by the respective movements of the fine pointing and the super pointing. Since the fine pointing needs to maintain the receiving locking and cannot be arbitrarily changed, a fixed beam deflection angle can only be introduced by adjusting the movement angle of the super pointing to compensate for the optical axis deviation existing in the system. In other words, adjusting the transceiving coaxiality is actually adjusting the movement angle of the super pointing. When the transmitting optical axis is parallel to the receiving optical axis, the state of the system at this time is defined as the "transceiving coaxial" state, and the control instruction reference point (i.e. the servo zero position) corresponding to the super pointing at this time is calibrated as the transceiving coaxial point of the system.

[0052] Specifically, the movement angle of the super pointing can be decomposed into the movement angles in the X-axis and Y-axis directions. By coordinating and adjusting the movement angles in the two directions, the system can reach the "transceiving coaxial" state in which the transmitting optical axis is parallel to the receiving optical axis. At this time, the system records the control instruction values corresponding to the X-axis and Y-axis, and defines the pair of values (X0, Y0) as the servo zero position, which is the "transceiving coaxial point". Therefore, the transceiving coaxial point is essentially a two-dimensional control parameter group (X0, Y0), rather than a specific physical position. In subsequent work, the system maintains the transceiving coaxiality by locking the control instruction of the super pointing around this point.

[0053] The receiving efficiency can reflect the energy of the light signal of a certain intensity transmitted by another laser communication terminal, which is effectively recognized and utilized by the laser communication terminal. There are mainly two ways to measure the receiving efficiency, i.e. the average energy of the light spot (referred to as "light spot energy" or "energy") in the tracking camera or the PA input value coupled into the terminal receiving optical fiber. Among them, the PA input value is an index for detecting the intensity of the optical signal in the receiving optical fiber, and the unit is dB. The larger the PA input value is, the higher the intensity of the optical signal in the receiving optical fiber is, and the better the communication quality is. If the PA input value is lower than the communication sensitivity threshold, the optical signal in the receiving optical fiber cannot be used to realize communication. In the embodiments of the present application, the efficiency is mainly measured by the light spot energy, and in other embodiments, any one or both of the two signals can be used for collaborative judgment, for example, first judge whether it is necessary to perform coaxial optimization based on the PA input value, if necessary, further calculate the light spot energy, and if not, directly record the current transceiving coaxial point.

[0054] It can be understood that the spot energy and the PA value, which are essentially positively correlated with the receiving efficiency, can be used as the feedback signal of the optimization process of the application. In the embodiment of the application, the entire optimization process is completed only by relying on the spot energy. As a preferred, the spot energy can be used for real-time control of the optimization process, and the PA value can be used for final verification of the optimization result to avoid misjudgment and further improve the accuracy of control.

[0055] The two laser communication terminals communicate through optical signals. When the PA input of the A terminal and the PA input of the B terminal both reach above the communication sensitivity threshold, the A terminal and the B terminal can communicate with each other. Therefore, the establishment of the laser communication link requires that the transmitting optical axis and the receiving optical axis of the two terminals are respectively aligned with the receiving optical axis and the transmitting optical axis of the other terminal.

[0056] In actual operation, two situations often occur. In one situation, the A terminal has poor transceiver coaxiality, but the B terminal has good transceiver coaxiality (its transmitting optical axis is approximately equal to its receiving optical axis). By adjusting the super-sight of the A terminal, its transmitting optical axis is aligned with the receiving optical axis of the B terminal, so that the receiving efficiency of the B terminal is the highest. However, when the receiving efficiency of the B terminal reaches the maximum, due to the poor transceiver coaxiality of the A terminal itself, the receiving optical axis of the A terminal deviates from the transmitting optical axis of the B terminal, thereby causing the receiving efficiency of the A terminal to be low. In another situation, when both the two laser communication terminals have transceiver coaxiality errors, at least one of the two laser communication terminals cannot simultaneously align its receiving optical axis and transmitting optical axis with the transmitting optical axis and receiving optical axis of the other terminal. This not only causes the receiving efficiency of at least one of the two laser communication terminals to be low, but also can even cause the communication link to be unable to be established.

[0057] In the above two situations, the two laser communication terminals have realized mutual tracking, that is, the two laser communication terminals have captured the optical signals transmitted by the other terminal. However, because the receiving efficiency is low (the PA input value is low) or cannot meet the requirement of realizing mutual communication, at this time, it is necessary to optimize the transceiver coaxiality of the two laser communication terminals, that is, to calibrate, to ensure the stable performance of the communication link.

[0058] To this end, in the calibration of the laser communication system, the drive component of the local super-sight is controlled to perform a sinusoidal motion at a specific frequency with the off-line calibrated coaxial point as the center. When the sinusoidal motion makes the local transmitting optical axis deviate from the receiving optical axis of the peer, the spot energy in the camera of the peer will decrease until the spot energy in the camera of the peer is weakest at the peak or valley of the sinusoidal wave; when the sinusoidal motion makes the local transmitting optical axis best align with the receiving optical axis of the peer, the spot energy in the camera of the peer is highest at the zero-crossing point of the sinusoidal wave. Therefore, when the super-sight performs the sinusoidal motion, the optical power received by the peer (corresponding to the spot energy in the camera of the peer) also periodically changes at the same frequency. The physical mechanism is that there is a certain phase relationship between the optical power change signal and the sinusoidal drive signal of the super-sight. When the local transmitting optical axis deviates from the best coaxial point, the peak of the optical power will stably appear in the phase of the wave peak or valley of the drive signal, which directly indicates the direction of the deviation. Based on this, the information interaction is performed through modulation and demodulation to realize the automatic optimization of the coaxiality of the transmitting and receiving.

[0059] The optimization method of the application is that one end (such as the A terminal) modulates the change of its own optical signal receiving performance index (i.e. the alignment state reflected by the above-mentioned phase relationship) onto its transmitting light and informs the other end (such as the B terminal) by assigning different modulation frequencies (such as N1 and N2) to "enhancement" and "weakening", and the other end adjusts its transmitting optical axis accordingly, thereby optimizing the receiving efficiency of the former (such as the A terminal).

[0060] Specifically, the drive component of the super-sight in the A terminal performs a sinusoidal motion at a certain frequency, and the frequency is used as a carrier to represent its own receiving state information; the B terminal detects that the frequency of the change of the spot energy detected by the tracking camera is the same as the frequency at which the super-sight of the A terminal operates, and by demodulating the frequency information, the A terminal can know the receiving state information it wants to transmit. The B terminal adjusts the angle of its own transmitting optical axis according to the information, thereby optimizing the receiving efficiency of the A terminal, and further optimizing the coaxiality of the transmitting and receiving of the whole system. The frequency can be used to carry specific information, for example, the frequency N1 represents that the spot energy in the camera is weakened, i.e. the coaxiality of the transmitting and receiving is deteriorated; the frequency N2 represents that the spot energy in the camera is enhanced, i.e. the coaxiality of the transmitting and receiving is improved.

[0061] Specifically, the A terminal periodically samples the spot energy of its tracking camera, and if it finds that the energy is weakened, it controls the super-sight to perform a sinusoidal motion at the frequency of N1 Hz with the off-line calibrated coaxial point as the center; if it finds that the energy is enhanced, it controls the super-sight to perform a sinusoidal motion at the frequency of N2 Hz. The motion curve is as shown in FIG. 1. Figure 3

[0062] ​The spot energy in the camera of the B terminal will change with the same frequency as the modulation movement of the light axis of the A terminal, and the energy change is as shown in FIG. 8. Figure 4 The B terminal can use the FFT method to solve the frequency information (N1 or N2) carried by the B terminal camera spot energy change, and the solving result is as shown in FIG. 9. Figure 5 Thus, the functions of the A terminal generating a modulation signal and the B terminal solving the signal information are realized.

[0063] It can be understood that the movement angle of the super-sighting can be decomposed into two components on the X axis and the Y axis. By adjusting the two axes (X axis and Y axis) of the driving part in the super-sighting, the two-dimensional movement angle of the galvanometer in the super-sighting can be controlled, and then the deflection angle of the light axis is controlled, that is, the pointing angle of the outgoing light beam in space is controlled.

[0064] In the actual optimization process, one axis (for example, the X axis) can be scanned, and the other axis (for example, the Y axis) can generate a modulation signal. When a certain switching condition is met, the functions of the two axes are switched, that is, the axis originally used for scanning makes a sinusoidal movement to generate a modulation signal, and the axis originally used for generating a modulation signal performs scanning. Thus, the precise adjustment of the deflection angle of the light axis is realized.

[0065] For example, the scanning axis of the B terminal will first start moving in the positive direction, and will move a certain distance in each sampling period. When the frequency information of the A terminal obtained by solving is N2 indicating "energy increase", it indicates that the co-axiality of the B terminal is getting better, and the scanning axis of the B terminal will continue to scan in the current direction. When the frequency information of the A terminal obtained by solving is N1 indicating "energy decrease", it indicates that the co-axiality of the B terminal is getting worse, and continuing the current scanning movement direction will lead to the decrease of the co-axiality of the B terminal. Therefore, the scanning axis of the B terminal needs to scan in the opposite direction.

[0066] During the movement of the scanning axis of the A terminal, the signal from the B terminal is always N2 (energy increase) before reaching the target coaxial point; after reaching the target coaxial point, the signal from the B terminal will become N1 (energy decrease) by continuing to scan forward. Therefore, the logic of switching the scanning axis and the modulation signal axis can be set as follows: when the frequency information of the B terminal changes from N2 to N1 is identified during the scanning process of the A terminal, the switching is performed. At this time, the A terminal records the current scanning axis position as the target coaxial point in the current direction, and switches the function to the modulation axis to generate a modulation signal starting from the target coaxial point; at the same time, the original modulation axis is switched to the scanning axis, and a new scanning in the orthogonal direction starting from the target coaxial point is performed.

[0067] The embodiment 2 discloses a beacon-free optical laser communication terminal transceiving coaxiality online optimization method, which comprises the following steps: obtaining a receiving performance index for reflecting optical signal receiving efficiency of a terminal; determining a modulation frequency according to a change trend of the optical signal receiving performance index; and controlling a leading aiming mechanism of the terminal to periodically move at the modulation frequency to emit an optical signal carrying modulation frequency information to a terminal laser communication terminal.

[0068] The modulation frequency information is used to indicate a scanning direction of the leading aiming mechanism of the terminal. The method can optimize the alignment between a transmitting optical axis of the terminal laser communication terminal and a receiving optical axis of the terminal laser communication terminal, so as to optimize the optical signal receiving efficiency of the terminal, thereby completing online optimization of the transceiving coaxiality of the terminal.

[0069] The leading aiming mechanism of the laser communication terminal has two orthogonal movement axes, and the periodic movement for realizing the modulation function is performed by one of the movement axes.

[0070] Further, the method further comprises: controlling the other movement axis of the leading aiming mechanism to perform a scanning function, and switching the functions performed by the two movement axes when a preset condition is met.

[0071] Further, the method further comprises: stopping the optimization when the receiving performance index reaches a preset target, and recording a control instruction value of the leading aiming mechanism as an updated transceiving coaxial point.

[0072] The method can be synchronously executed on the terminal laser communication terminal, and the online optimization of the transceiving coaxiality of the laser communication terminal is completed by the synchronous execution of the two terminals.

[0073] The specific steps of the method in the embodiment 2 are described in the related description of the embodiment 1, and as a person skilled in the art should clearly understand, this part will not be described again.

[0074] In combination with Figure 6 A terminal generates an optical signal, the transmitting optical axis of the B terminal is adjusted, and the receiving efficiency of the A terminal is optimized, for example, the transceiving coaxiality of the A terminal is optimized, and the optimization method mainly comprises the following steps:

[0075] Step 1: The A terminal periodically samples the energy of a light spot detected by a leading aiming camera, and selects a modulation frequency according to the energy change: if the energy of the camera is detected to increase, N2 is used as the frequency of the sine movement of the leading aiming; if the energy of the camera is detected to decrease, N1 is used as the frequency of the sine movement of the leading aiming. For example, N1 = 1 Hz, N2 = 2 Hz; or N1 = 5 Hz, N2 = 6 Hz.

[0076] Step 2: Control the super-sight of the A terminal to be centered on the off-line test transceiving coaxial point, and make sinusoidal motion in the modulation axis (such as X axis) direction with the frequency determined in step 1, so as to modulate the light signal with frequency information and send it to the universe space through the transmitting light path.

[0077] Step 3: The B terminal receives the light signal with frequency information transmitted by the A terminal through the receiving light path, and uses the FFT algorithm to solve the received light signal, so as to solve the frequency information (N1 or N2) in the light signal.

[0078] Step 4: The B terminal adjusts its transmitting light axis according to the solved frequency information, which can be realized by controlling the motion angle of the scanning axis of the super-sight. If the solved frequency information is N2 (representing that the energy of the A terminal becomes strong), the scanning axis of the super-sight of the B terminal continues to scan in the original direction; if the solved frequency information is N1 (representing that the energy of the A terminal becomes weak), the scanning axis of the super-sight of the B terminal immediately reverses the motion, so as to optimize the receiving efficiency of the A terminal.

[0079] Repeat the above steps 1 to 4, and when the switching condition is met, switch the scanning axis and the modulation axis functions of the super-sights of the A and B terminals, until the receiving efficiency of the A terminal is optimal.

[0080] It can be understood that the above process is the flow of optimization of one end, and the same flow is simultaneously performed on the other end. Figure 7 As shown in the software implementation flowchart of the double-end transceiving coaxiality optimization shown in the combination

[0081] It is worth noting that in laser communication, the receiving efficiency of the local terminal is affected by the transceiving coaxiality of the opposite terminal. It is worth noting that in the present application, the receiving efficiency of the local terminal can be improved by optimizing the transceiving coaxiality of the opposite terminal, and the local terminal can also perform online optimization of the transceiving coaxiality of the local terminal while cooperating with the opposite terminal to perform online optimization of the transceiving coaxiality of the opposite terminal, so as to improve the receiving efficiency of the opposite terminal. Thus, the communication efficiency of the two terminals can be greatly improved, and the communication quality can be ensured.

[0082] It can be understood that, Figure 7 In the combination, the PA input value and the communication sensitivity threshold are used as the judgment condition for triggering optimization. When the PA input value is less than the communication sensitivity threshold, the optimization is triggered, the terminal calculates the energy of the light spot of the super-sight camera, and determines the frequency (N1 or N2) of the sinusoidal motion of the modulation axis based on the energy change, and sends the light signal carrying the frequency information to the opposite terminal.

[0083] In summary, the application uses the driving function of the super sight, without extra beacon light path and calibration sighting scope and other redundant function modules, to realize the transmission-reception coaxiality optimization of the laser communication terminal online. Compared with offline adjustment of transmission-reception coaxiality, the application can optimize the transmission-reception coaxiality in real time; compared with manual adjustment, the application can realize automatic adjustment of the transmission-reception coaxiality, only needs to send the parameters required for satellite control program running and the instruction for starting the online optimization function, greatly improves the utilization efficiency of the in-orbit window period. Moreover, according to the actual measurement, the application can optimize the PA input value of the receiving light path, and the optimization amplitude can reach more than 3dB.

[0084] The cooperative optimization mechanism based on "modulation-solution" proposed by the application has stronger robustness and does not depend on a complex optical path model; realizes real "no beacon light, no new optical path" online optimization, fundamentally improves the system reliability; realizes full-automatic, in-orbit real-time optimization, greatly improves the task efficiency and in-orbit maintenance; the optimization effect is remarkable, and has clear engineering application value.

[0085] Finally, it should be noted that although the embodiments of the application are described above in combination with the drawings, the application is not limited to the above specific embodiments and application fields, and the above specific embodiments are only illustrative and guiding, but not limiting. Those skilled in the art can make many forms under the inspiration of the present application without departing from the scope of the claims of the application, and these all belong to the protection of the application.

Claims

1. A method for online optimization of coaxiality of laser communication terminal transceiver, characterized in that, Includes the following steps: Receive optical signals carrying modulation frequency information transmitted by the laser communication terminal at the other end; The modulation frequency information is calculated from the optical signal; the modulation frequency information is determined by the peer laser communication terminal based on the changing trend of the receiving performance indicators that it acquires to reflect its own optical signal receiving efficiency. The scanning direction of the forward aiming mechanism of the local laser communication terminal is adjusted according to the calculated modulation frequency information in order to achieve online optimization of the coaxiality of the local laser communication terminal. The modulation frequency information in the optical signal transmitted by the peer laser communication terminal includes a first frequency or a second frequency; wherein, the first frequency is used to instruct the forward aiming mechanism of the local laser communication terminal to maintain the current scanning direction, and the second frequency is used to instruct the forward aiming mechanism of the local laser communication terminal to move in the opposite direction to the current scanning direction.

2. The method according to claim 1, characterized in that, It also includes the following steps: Obtain receiving performance indicators that reflect the optical signal receiving efficiency of the local laser communication terminal; A modulation frequency is determined based on the changing trend of the aforementioned receiving performance indicators; The aiming mechanism of the local laser communication terminal is controlled to move periodically at the modulation frequency to transmit an optical signal carrying modulation frequency information to the remote laser communication terminal. The modulation frequency information is used to instruct the remote laser communication terminal to control the scanning direction of its aiming mechanism, so as to achieve online optimization of the coaxiality of the remote laser communication terminal.

3. The method according to claim 2, characterized in that, The periodic motion is a sine or cosine motion.

4. The method according to claim 2, characterized in that, The periodic motion is centered on the offline calibrated transceiver coaxial point.

5. The method according to any one of claims 1 to 4, characterized in that, The receiving performance indicators include at least one of the average spot energy and the optical power input PA value; the average spot energy is obtained by the tracking camera of the laser communication terminal; the optical power input PA value is defined as the PA value obtained by the optical signal processor after being coupled to the receiving optical fiber of the laser communication terminal.

6. The method according to any one of claims 1 to 4, characterized in that, The laser communication terminal's forward aiming mechanism has two orthogonal motion axes; one is used to perform periodic motion to achieve modulation, and the other is used to achieve scanning. The functions of the two motion axes are switched when preset conditions are met.

7. The method according to claim 6, characterized in that, The preset condition is that the trend of the receiving performance index changes from enhancement to weakening.

8. The method according to any one of claims 1 to 4, characterized in that, The modulation frequency information is calculated from the optical signal using the Fast Fourier Transform (FFT) algorithm.

9. The method according to any one of claims 1 to 4, characterized in that, Also includes: When the receiving performance index reaches the preset target, the coaxiality optimization of the transmitting and receiving is stopped, and the current control command value of the advanced aiming mechanism is recorded as the updated transmitting and receiving coaxial point.

10. A method for online optimization of the coaxiality of a laser communication terminal, characterized in that, Includes the following steps: Obtain receiving performance indicators that reflect the optical signal receiving efficiency of the local laser communication terminal; A modulation frequency is determined based on the changing trend of the aforementioned receiving performance indicators; The aiming mechanism of the local laser communication terminal is controlled to move periodically at the modulation frequency to transmit an optical signal carrying modulation frequency information to the remote laser communication terminal. The modulation frequency information is used to instruct the remote terminal to adjust the scanning direction of its aiming mechanism so as to achieve online optimization of the coaxiality of the remote laser communication terminal. The modulation frequency information in the optical signal transmitted by the local laser communication terminal includes a first frequency or a second frequency; wherein, the first frequency is used to instruct the forward aiming mechanism of the remote laser communication terminal to maintain the current scanning direction, and the second frequency is used to instruct the forward aiming mechanism of the remote laser communication terminal to move in the opposite direction to the current scanning direction.

11. A laser communication terminal, characterized in that, It includes a light source generator (1), a transmitting fiber (3), a receiving fiber (4), an optical signal processor (2), a coarse servo mechanism (7), an advanced aiming mechanism, a fine tracking mechanism, a tracking camera (8), and a controller (9); The advanced aiming mechanism has two orthogonal axes of motion, one of which is used to perform periodic motion to achieve the modulation function, and the other is used to perform the scanning function. The controller (9) is electrically connected to the tracking camera (8), the optical signal processor (2), the coarse servo mechanism (7), the advanced aiming mechanism and the fine tracking mechanism, respectively, and is used to execute the online optimization method for the coaxiality of the laser communication terminal as described in any one of claims 1 to 9 or claim 10.

12. The laser communication terminal as described in claim 11, characterized in that, Both the advanced aiming mechanism and the precision tracking mechanism are equipped with galvanometers and their driving components.

13. A laser communication system, characterized in that, include: At least two laser communication terminals; the laser communication terminal is the laser communication terminal as described in claim 11 or 12.

Images