Active polarization switching laser communication terminal, method and storage medium
Patent Information
- Application Number
- CN202611479480.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-09-22
- Publication Date
- 2026-11-03
Smart Images
Figure CN123034896A_ABST
Abstract
Description
Technical Field
[0001] This disclosure mainly relates to the field of space laser communication technology, and in particular to an active polarization switching laser communication terminal, method and storage medium. Background Technology
[0002] In the process of establishing and networking space laser communication links, the polarization state of the light beam can be used to achieve signal isolation and anti-interference transmission. To realize a polarization-isolated beam splitting mechanism, the laser communication terminal needs to have the ability to switch between two working states (A and B) to complete the link establishment and networking between the two ends. Under this mechanism, the two communicating parties must maintain complementary states; that is, when one end is in state A, the other end must be in state B, and vice versa, thus forming an effective polarization-matched link. To achieve the above-mentioned interlocked switching of states, existing technologies typically employ polarization state control methods using quarter-wave plates or half-wave plates as the core control elements. These plates are mechanically or electrically controlled to enter or exit the optical path, thereby achieving the conversion between two orthogonal polarization states.
[0003] However, the aforementioned existing technologies have several drawbacks. First, the fixed polarization state pairing mechanism severely limits network flexibility. Because existing polarization-splitting laser communication terminals employ an A / B state complementary matching mechanism, establishing a communication link between any two terminals requires ensuring that the transmitted polarization state at one end matches the received polarization state at the other. After a satellite enters orbit, if a terminal malfunctions or a new satellite joins the network, it becomes impossible to establish a link with on-orbit terminals that have different polarization references. As the scale of space laser communication networks expands, this polarization island problem is increasingly becoming one of the main bottlenecks restricting network robustness and scalability.
[0004] Therefore, there is an urgent need for a technical solution that can adaptively establish a link with a peer terminal with any polarization reference. Summary of the Invention
[0005] The technical problem to be solved by this disclosure is to provide an active polarization switching laser communication terminal, method and storage medium, which solves the technical problems of limited networking flexibility and low link establishment efficiency caused by the requirement of fixed polarization state pairing for link establishment in existing polarization split laser communication terminals.
[0006] To address the aforementioned technical problems, this disclosure provides an active polarization-switching laser communication terminal, comprising: a main controller, a polarization-maintaining fiber circulator, a polarization controller, and a collimator; wherein the polarization-maintaining fiber circulator has a first port, a second port, and a third port, the first port being connected to the transmitting end of the main controller, and the third port being connected to the receiving end of the main controller; the first end of the polarization controller is connected to the second port of the polarization-maintaining fiber circulator, and the second end of the polarization controller is connected to the collimator; the polarization controller is used to apply a polarization state transformation to a beam transmitted in the optical path between the polarization-maintaining fiber circulator and the collimator, the beam including a transmitted beam and a received beam; the main controller is configured to send a polarization state pre-switching command to the polarization controller before link establishment, based on the polarization reference state of the peer laser communication terminal; the polarization controller changes the polarization state of the transmitted beam according to the polarization state pre-switching command, so that the polarization state of the transmitted beam matches the polarization reference state.
[0007] In some embodiments, the main controller is further configured to: after the laser communication terminal establishes a bidirectional link with the peer laser communication terminal, iteratively adjust the driving voltage of the polarization controller using the second received optical power value as a feedback quantity, so that the second received optical power value reaches its maximum value; the second received optical power value is the signal optical power value received by the peer laser communication terminal from the laser communication terminal.
[0008] In some embodiments, the system further includes: a forward aiming generator, a tracking communication beam splitter, a fine-tracking fast-reflecting mirror, a transceiver telescope, and a coarse-tracking mechanism arranged sequentially along the optical path; wherein, the main controller is further configured to: control the fine-tracking fast-reflecting mirror to perform nutation scanning before iteratively adjusting the driving voltage of the polarization controller, so that the first received optical power value reaches its maximum value; the first received optical power value is the signal optical power value received by the laser communication terminal from the peer laser communication terminal.
[0009] In some embodiments, the device further includes: a capture tracking detector for connecting to the tracking output of the tracking communication beam splitter to receive the tracked optical signal after beam splitting and generate a nutation tracking error signal.
[0010] In some embodiments, the main controller is further configured to iteratively adjust the drive voltage of the polarization controller using a stochastic parallel gradient descent algorithm.
[0011] In some embodiments, when the main controller executes the stochastic parallel gradient descent algorithm, it includes the following steps: initializing the driving voltage of the polarization controller and setting the perturbation amount and gain coefficient; iteratively executing the following steps until the second received optical power value meets a system preset threshold: generating a random perturbation voltage, calculating a positive perturbation voltage and a negative perturbation voltage based on the random perturbation voltage and the current driving voltage; sequentially applying the positive perturbation voltage and the negative perturbation voltage to the polarization controller, and recording the first value and the second value of the corresponding second received optical power value respectively; calculating a gradient estimate based on the difference between the first value and the second value, updating the driving voltage based on the gradient estimate, the perturbation amount and the gain coefficient; applying the updated driving voltage to the polarization controller, and recording the corresponding second received optical power value.
[0012] In some embodiments, the main controller is further configured to: according to a preset time-division protocol, cause the laser communication terminal and the peer laser communication terminal to alternately perform polarization state closed-loop adjustment, and allow only one laser communication terminal to actively adjust the driving voltage of its polarization controller at any given time.
[0013] In some embodiments, the polarization controller is an all-fiber electrically controlled polarization controller.
[0014] To address the aforementioned technical problems, this disclosure provides an active polarization switching method for a laser communication terminal, applicable to a laser communication terminal including a main controller, a polarization-maintaining fiber circulator, a polarization controller, and a collimator. The polarization controller is disposed in the common transmit-receive optical path between the polarization-maintaining fiber circulator and the collimator, and includes the following steps: Before establishing the link, obtain the polarization reference state of the laser communication terminal at the other end; Based on the polarization reference state, a polarization state pre-switching command is sent to the polarization controller; The polarization controller changes the polarization state of the transmitted beam in the common optical path of transmission and reception according to the polarization state pre-switching command, so that the polarization state of the transmitted beam matches the polarization reference state.
[0015] In some embodiments, the method further includes the following steps: establishing a bidirectional link with the peer laser communication terminal; iteratively adjusting the driving voltage of the polarization controller using the second received optical power value as a feedback quantity, so that the second received optical power value reaches its maximum value; the second received optical power value is the signal optical power value received by the peer laser communication terminal from the laser communication terminal.
[0016] In some embodiments, before performing iterative adjustment of the drive voltage of the polarization controller, the method further includes: controlling the fine-tracking fast-reflection mirror to perform nutation scanning to make the first received optical power value reach a maximum value; the first received optical power value is the signal optical power value received by the laser communication terminal from the peer laser communication terminal.
[0017] In some embodiments, a stochastic parallel gradient descent algorithm is used to iteratively adjust the driving voltage of the polarization controller.
[0018] In some embodiments, the stochastic parallel gradient descent algorithm includes the following steps: initializing the driving voltage of the polarization controller and setting the perturbation amount and gain coefficient; iteratively executing the following steps until the second received optical power value meets a system preset threshold: generating a random perturbation voltage, calculating a positive perturbation voltage and a negative perturbation voltage based on the random perturbation voltage and the current driving voltage; sequentially applying the positive perturbation voltage and the negative perturbation voltage to the polarization controller, and recording the first value and the second value of the corresponding second received optical power value respectively; calculating a gradient estimate based on the difference between the first value and the second value, updating the driving voltage based on the gradient estimate, the perturbation amount and the gain coefficient; applying the updated driving voltage to the polarization controller, and recording the corresponding second received optical power value.
[0019] In some embodiments, the method further includes: alternating polarization state closed-loop adjustment with the peer laser communication terminal according to a preset time-division protocol, allowing only one laser communication terminal to actively adjust the driving voltage of its polarization controller at any given time.
[0020] To address the aforementioned technical problems, this disclosure provides a computer-readable storage medium storing a computer program, which, when executed by the main controller of a laser communication terminal, causes the laser communication terminal to perform the methods described in this application.
[0021] Compared with the prior art, this disclosure has the following advantages: The active polarization switching laser communication terminal, method, and storage medium of this application insert a polarization controller into the shared optical path for transmission and reception between the polarization-maintaining fiber circulator and collimator. Before link establishment, the main controller sends a polarization state pre-switching command to the polarization controller based on the known polarization reference state of the peer laser communication terminal, so that the polarization state of the transmitted beam matches the polarization reference state of the peer. This allows the laser communication terminal to adaptively match the peer laser communication terminal in standard A state, standard B state, and any non-standard polarization state, thereby improving the networking flexibility and dynamic reconfiguration capability of the space laser communication network. Attached Figure Description
[0022] The accompanying drawings are included to provide a further understanding of this disclosure; they are incorporated into and form part of this disclosure. The drawings illustrate embodiments of this disclosure and, together with this specification, serve to explain the principles of this disclosure.
[0023] Figure 1 This is a network diagram of a traditional laser communication terminal.
[0024] Figure 2 This is an embodiment of an active polarization switching laser communication terminal disclosed herein.
[0025] Figure 3 This is a network diagram of a laser communication terminal according to an embodiment of the present disclosure.
[0026] Figure 4 This is a flowchart of an active polarization switching method for a laser communication terminal according to an embodiment of the present disclosure.
[0027] Figure 5 This is a flowchart of a laser communication terminal performing nutation scanning according to an embodiment of the present disclosure.
[0028] Figure 6 This is a flowchart of the closed-loop fine-tuning stage of polarization state execution by a laser communication terminal according to an embodiment of the present disclosure.
[0029] Figure 7 This is a flowchart of a stochastic parallel gradient descent algorithm according to an embodiment of the present disclosure. Detailed Implementation
[0030] The technical solutions of the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this disclosure, and not all embodiments. Based on the embodiments of this disclosure, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this disclosure.
[0031] Figure 1 This is a network diagram of a traditional laser communication terminal. (Example) Figure 1 As shown, space laser communication units 1, 2, 3, and 4 are from the first manufacturer and operate in A / B polarization mode; space laser communication units 5, 6, 7, and 8 are from the second manufacturer and operate in A' / B' polarization mode. The definition of A' / B' polarization mode differs from that of A / B polarization mode. For example, some systems use left / right circularly polarized or elliptically polarized light for beam splitting, while others use orthogonally linearly polarized light for isolation. The above network architecture has limitations at the following two levels: First, there is insufficient cross-manufacturer / cross-system compatibility. Due to the different polarization state definitions and beam splitting methods used by different manufacturers, when terminals from different manufacturers or using different polarization modes attempt to establish a link, the incompatibility between the A / B polarization working state and the A' / B' polarization working state definition prevents space laser communication devices 1, 2, 3, and 4 from establishing effective communication with space laser communication devices 5, 6, 7, and 8, resulting in the network being fragmented into multiple independent subnets.
[0032] Second, single-point failures limit network topology. When space laser communication device 2 (B state) fails, space laser communication device 1 (A state) and space laser communication device 4 (A state) are both in the same state. Since traditional polarization splitting schemes require the two communicating parties to be in complementary polarization states, space laser communication device 1 and space laser communication device 4 cannot directly establish a communication link, which severely limits the network topology reconstruction capability.
[0033] The above factors together result in significant deficiencies in the flexibility, compatibility, and robustness of existing laser communication terminal networks.
[0034] To address the shortcomings of the existing technologies, this disclosure proposes an active polarization-switching laser communication terminal. This terminal utilizes a fully fiber-optic electrically controlled polarization controller in the shared optical path between the polarization-maintaining fiber circulator and the transmit / receive collimator. This allows a single terminal to actively switch the polarization state of its emitted beam based on the polarization reference state of the peer laser communication terminal, achieving adaptive matching with peer terminals of arbitrary polarization configurations. This overcomes cross-manufacturer / cross-system compatibility barriers and breaks the rigid constraint that terminals of the same polarization cannot be paired. Furthermore, through inter-satellite optical power feedback closed-loop fine-tuning and time-division collaborative control, it achieves flexible link establishment and dynamic networking without pre-configuration, significantly improving the flexibility, compatibility, and robustness of space laser communication networks.
[0035] Figure 2 This is an embodiment of an active polarization-switching laser communication terminal disclosed herein. For example... Figure 2 As shown, the active polarization switching laser communication terminal includes: a main controller 101, a polarization-maintaining fiber circulator 102, a polarization controller 103, and a collimator 104.
[0036] The main controller 101 is used to generate the transmitted signal light, demodulate the received signal light, and execute the polarization adaptive control algorithm. The main controller 101 has a transmitting end and a receiving end. Its transmitting end is connected to the first port of the polarization-maintaining fiber circulator 102 through a transmitting optical fiber, and its receiving end is connected to the third port of the polarization-maintaining fiber circulator 102 through a receiving optical fiber.
[0037] The polarization-maintaining fiber circulator 102 has a first port, a second port, and a third port. The first port serves as the transmit input and is connected to the transmitter of the main controller 101; the second port serves as a common port and is connected to the first terminal of the polarization controller 103; the third port serves as the receive output and is connected to the receiver of the main controller 101. The polarization-maintaining fiber circulator 102 is used to isolate the transmit and receive optical paths directionally on the common optical path. The transmit optical signal enters from the first port and is output only from the second port, and the receive optical signal enters from the second port and is output only from the third port, thereby achieving physical isolation and combining separation of the transmit and receive optical paths.
[0038] The first end of the polarization controller 103 is connected to the second port of the polarization-maintaining fiber circulator 102, and the second end of the polarization controller 103 is connected to the collimator 104. The polarization controller 103 is disposed in the shared transmission and reception optical path between the polarization-maintaining fiber circulator 102 and the collimator 104, and is used to apply polarization state transformation to the beam transmitted in the shared optical path. The polarization controller 103 simultaneously performs the dual functions of transmission polarization state modulation and reception polarization state modulation: in the transmission path, the optical signal is transmitted from the polarization-maintaining fiber circulator 102 to the collimator 104 via the polarization controller 103, and the polarization controller 103 actively modulates the polarization state of the transmitted beam; in the reception path, the optical signal is transmitted from the collimator 104 to the polarization-maintaining fiber circulator 102 via the polarization controller 103, and the polarization controller 103 modulates the polarization state of the received beam.
[0039] In some embodiments, the polarization controller 103 is an all-fiber electrically controlled polarization controller, which applies stress or electric field to the optical fiber through an electrically controlled driving voltage to change the polarization state of the transmitted light, and has no mechanical moving parts.
[0040] Collimator 104 is connected to the second end of polarization controller 103 and is used to realize optical signal mode conversion between optical fiber and free space. In the transmission direction, it converts the guided wave mode in the optical fiber into a collimated beam in free space. In the reception direction, it couples the free space received beam into the optical fiber.
[0041] The main controller 101 is configured to send a polarization state pre-switching command to the polarization controller before link establishment, based on the polarization reference state of the peer laser communication terminal. The polarization controller 103 changes the polarization state of the emitted beam according to the polarization state pre-switching command, so that the polarization state of the emitted beam matches the polarization reference state.
[0042] In some embodiments, when the space laser communication terminal prepares to establish a link with the peer laser communication terminal, the main controller 101 first acquires the polarization reference state of the peer laser communication terminal. This polarization reference state is information that the main controller 101 has prior knowledge of before link establishment. Acquisition methods include, but are not limited to: uploading the polarization configuration information of each terminal in the network to the satellite terminal via ground station remote control uploading commands; distributing the network topology and polarization configuration information of each terminal within the constellation via inter-satellite network management protocol broadcasting; and querying the peer terminal's polarization reference state through ephemeris and terminal information databases. Before link establishment, since a communication link has not yet been established between the laser communication terminal and the peer laser communication terminal, it is impossible to obtain real-time polarization status information from the peer laser communication terminal through signaling interaction. Therefore, the aforementioned prior knowledge method ensures that the main controller 101 can obtain the polarization reference state of the peer laser communication terminal before link establishment. The polarization reference state can be a standard A polarization state (such as horizontal linear polarization), a standard B polarization state (such as vertical linear polarization), or a non-standard arbitrary polarization state (such as 45° linear polarization, circular polarization, or elliptical polarization, etc.). This disclosure does not impose any limitations on this.
[0043] After obtaining the polarization reference state of the peer laser communication terminal, the main controller 101 generates control instructions for the polarization controller 103 based on the polarization reference state. Specifically, the main controller 101 internally stores a polarization state-voltage mapping table or a polarization state-voltage mapping function. This table or function records the correspondence between the driving voltage combinations of the polarization controller 103 and the output polarization state. The main controller 101 obtains the driving voltage value required to match the polarization state of the polarization controller 103 by looking up the table or calculating based on the peer polarization reference state, and encodes this voltage value as a polarization state pre-switching instruction.
[0044] The main controller 101 sends the generated polarization state pre-switching command to the polarization controller 103. Upon receiving the command, the polarization controller 103 applies a corresponding electronically controlled drive signal to its internal polarization state modulation element according to the drive voltage value contained in the command. In some embodiments, when the polarization controller 103 is a piezoelectric ceramic extrusion type all-fiber polarization controller, the polarization controller 103 applies corresponding voltages to the four sets of piezoelectric ceramic drivers according to the drive voltage value, changing the polarization state of the transmitted light in the polarization-maintaining fiber through the stress birefringence effect, thus transforming the polarization state of the emitted beam from the current state to the target state. When the polarization controller 103 is a photoelectric effect-based all-fiber polarization controller, the polarization controller 103 modulates the polarization state of the transmitted light through the electro-optic effect, transforming the polarization state of the emitted beam to the target state.
[0045] After the polarization controller 103 completes the polarization state transformation, the emitted beam is emitted into free space through the collimator 104 with a polarization state that matches the polarization reference state, so that the laser communication terminal at the other end can receive the optical signal emitted by the laser communication terminal with the highest efficiency, thereby completing the polarization state pre-configuration before link establishment.
[0046] like Figure 1 As shown, the active polarization switching laser communication terminal also includes an advance aiming generator 105, a tracking communication beam splitter 106, a fine tracking fast reflection mirror 107, a transceiver telescope 108, and a coarse tracking mechanism 109 arranged sequentially along the optical path.
[0047] The input of the forward aiming generator 105 is connected to the output of the collimator 104. The forward aiming generator 105 compensates for the Doppler frequency shift and beam pointing pre-offset angle caused by inter-satellite relative motion. In inter-satellite laser communication, due to the relative motion between the two satellites, the receiver experiences a Doppler frequency shift, and the beam propagation direction also needs to consider the pre-offset angle caused by skewing aberration. The forward aiming generator 105 applies a forward deflection angle to the transmitted beam through a built-in fast-reflecting mirror or wedge prism group, ensuring that the transmitted beam accurately points to the receiving aperture of the receiving terminal even after considering the relative motion of the satellites. In the receiving direction, the forward aiming generator 105 compensates for the pointing deviation of the received beam in the opposite direction, ensuring that the received beam is correctly coupled into the collimator 104.
[0048] The input of the tracking communication beam splitter 106 is connected to the output of the look-ahead generator 105. The tracking communication beam splitter 106 is used to split the optical signal in the receiving optical path into two parts: communication light and tracking light, or to combine the communication light and tracking light in the transmitting optical path into a single beam. In the transmitting direction, the tracking communication beam splitter 106 combines the communication light from the autonomous controller 101 and the tracking light from the tracking light source into a single beam, which is then transmitted to the peer laser communication terminal via a subsequent optical path to ensure that the peer laser communication terminal can receive the optical signal containing tracking information for acquisition and tracking. In the receiving direction, the tracking communication beam splitter 106 splits the optical signal from the peer laser communication terminal into two paths: one is the communication light, which travels along the main optical path through the look-ahead generator 105 and collimator 104 into the polarization-maintaining fiber circulator 102, and is finally demodulated by the receiving detection module of the main controller 101; the other is the tracking light, which is reflected to the photosensitive surface of the acquisition and tracking detector 110. The capture and tracking detector 110 performs photoelectric conversion and signal processing on the received tracking light signal, and generates a tracking error signal based on the position information of the light spot on the focal plane of the detector.
[0049] The incident surface of the precision tracking fast reflector 107 is connected to the output of the tracking communication beam splitter 106. The precision tracking fast reflector 107 is used to compensate for beam pointing deviations caused by satellite platform vibration and attitude jitter. In the spaceborne environment, the satellite platform has various vibration sources of different frequencies and amplitudes. These vibrations cause high-frequency jitter in the beam pointing, thereby reducing the coupling efficiency of space light to the receiving fiber. In this disclosure, the precision tracking fast reflector 107 also functions as a nutation adjustment actuator. During nutation scanning, the precision tracking fast reflector 107 applies sinusoidal perturbation signals along two mutually orthogonal axes, causing the beam to trace a tiny circular trajectory in space, thereby optimizing the space light-fiber coupling angle. "Nutation" in the field of space laser communication refers to an active scanning technology used for precise calibration and tracking. Its core is to make the beam perform tiny, regular circular movements. This method can achieve high-precision beam alignment without complex position detectors. In the transmission direction, the precision tracking quick-reflecting mirror 107 adjusts the mirror angle in real time according to the pointing error signal provided by the main controller 101 to correct the high-frequency pointing deviation of the transmitted beam; in the receiving direction, the precision tracking quick-reflecting mirror 107 adjusts the mirror angle in real time according to the tracking error signal provided by the acquisition and tracking detector 110 to stably reflect the beam received from the transceiver telescope 108 to the tracking communication beam splitter 106 and subsequent optical paths.
[0050] The incident end of the transceiver telescope 108 is connected to the output end of the precision tracking mirror 107. The transceiver telescope 108 is used to realize the beam expansion and collimation of the emitted beam and the beam focusing and collection of the received beam.
[0051] A coarse tracking mechanism 109 is connected to the periphery or front end of the transceiver telescope 108. The coarse tracking mechanism 109 is used to achieve large-scale coarse pointing acquisition and tracking between satellites. In the initial link establishment phase, the coarse tracking mechanism 109 calculates the position of the peer satellite based on ephemeris data and points the optical axis of the transceiver telescope 108 to the expected position of the peer satellite, completing the initial acquisition. In the link maintenance phase, the coarse tracking mechanism 109 maintains the pointing over a large area with a low bandwidth based on the coarse tracking error signal provided by the acquisition and tracking detector, ensuring that the peer satellite is always within the field of view of the transceiver telescope 108. The coarse tracking mechanism 109 and the fine tracking quick-reflection mirror 107 together constitute a coarse-fine two-stage tracking system. The coarse tracking mechanism 109 is responsible for large-scale, low-bandwidth pointing, while the fine tracking quick-reflection mirror 107 is responsible for small-scale, high-bandwidth pointing correction. Together, they achieve high-precision, large dynamic range beam pointing control.
[0052] The active polarization switching laser communication terminal also includes a capture and tracking detector 110. The capture and tracking detector 110 is connected to the tracking output of the tracking communication beam splitter 106, and is used to receive the tracking light signal split by the tracking communication beam splitter 106, and generate error signals for capture, tracking and nutation scanning based on the tracking light signal.
[0053] In the transmitting optical path, the optical signal sequentially passes through collimator 104, forward aiming generator 105, tracking communication beam splitter 106, precision tracking fast mirror 107, transceiver telescope 108, and coarse tracking mechanism 109 before being transmitted into free space. In the receiving optical path, the optical signal sequentially passes through coarse tracking mechanism 109, transceiver telescope 108, precision tracking fast mirror 107, tracking communication beam splitter 106, forward aiming generator 105, and collimator 104 before being coupled into polarization-maintaining fiber circulator 102.
[0054] This disclosure places the polarization controller in the shared transmit and receive optical path between the polarization-maintaining fiber circulator and the collimator. Before link establishment, the main controller sends a polarization state pre-switching command to the polarization controller based on the known polarization reference state of the peer laser communication terminal, ensuring that the polarization state of the transmitted beam matches the polarization reference state of the peer. On the one hand, this fundamentally breaks the rigid constraint that traditional A / B terminals must be used in pairs, allowing a single terminal to adaptively match peer laser communication terminals in standard A state, standard B state, and any non-standard polarization state, significantly improving the networking flexibility and dynamic reconfiguration capability of space laser communication networks. On the other hand, by using a single polarization controller to simultaneously serve both transmit and receive optical paths, this avoids the discrete design of configuring polarization devices separately for the transmit and receive branches in traditional schemes, greatly reducing the number of optical components and lowering the system size, weight, insertion loss, and cost.
[0055] Figure 3 This is a network diagram of a laser communication terminal according to an embodiment of this disclosure. Figure 3 As shown, the space laser communication terminal 2 is the active polarization switching laser communication terminal proposed in this disclosure. Figure 3 The polarization states used by each space laser communication terminal are shown. Space laser communication terminal 1 and space laser communication terminal 4 use the standard A polarization state, space laser communication terminal 3 uses the standard B polarization state, space laser communication terminal 5 and space laser communication terminal 8 use the non-standard A' polarization state, and space laser communication terminal 6 and space laser communication terminal 7 use the non-standard B' polarization state.
[0056] like Figure 3As shown by the solid lines in the diagram, space laser communication terminal 2 can establish bidirectional communication links with space laser communication terminals 1 and 4 using standard A polarization, with space laser communication terminal 3 using standard B polarization, and with space laser communication terminal 5 using non-standard A' polarization, as well as with space laser communication terminal 7 using non-standard B' polarization. In other words, a single space laser communication terminal 2 can simultaneously be compatible with peer space laser communication terminals using standard A, standard B, and any non-standard polarization (such as non-standard A' or non-standard B' polarization). This networking architecture fully demonstrates the flexibility and robustness advantages of this disclosed solution in space laser communication networks. At the network dynamic reconfiguration level, when a new satellite terminal (regardless of its polarization system) needs to access the network, the terminal of this disclosed solution can adaptively complete polarization matching and establish a link, significantly improving the efficiency of constellation networking and dynamic reconfiguration. In terms of network fault tolerance and self-healing, when some satellites in the network experience link interruptions due to orbital changes or malfunctions, adjacent terminals disclosed herein can quickly establish alternative links without ground intervention, significantly improving the network's autonomous operation capability and on-orbit reliability.
[0057] In some embodiments, the main controller is configured to support at least two operating modes: a pre-switching mode before link establishment and a closed-loop fine-tuning mode after link establishment. In pre-switching mode, the main controller sends a pre-switching command to the polarization controller based on the known polarization reference state of the peer end, setting the driving voltage to a value matching the peer polarization reference. This allows the polarization state of the emitted beam to quickly switch to a range approximately receivable by the peer end, ensuring that both parties can complete acquisition and bidirectional link establishment under coarse matching conditions. In closed-loop fine-tuning mode, after the laser communication terminal establishes a bidirectional link with the peer laser communication terminal, the main controller uses the received optical power value returned by the peer laser communication terminal as feedback and employs an iterative optimization algorithm to continuously fine-tune the polarization controller driving voltage, maximizing the received optical power of the peer laser communication terminal.
[0058] In some embodiments, the main controller 101 is further configured to: after establishing a bidirectional link between the laser communication terminal and the peer laser communication terminal, iteratively adjust the driving voltage of the polarization controller using the second received optical power value as feedback, so that the second received optical power value reaches its maximum value; the second received optical power value is the signal optical power value received by the peer laser communication terminal from the laser communication terminal. In some embodiments, the driving voltage of the polarization controller is iteratively adjusted using the Stochastic Parallel Gradient Descent (SPGD) algorithm.
[0059] In some embodiments, the main controller 101 is further configured to: control the fine-tracking fast-reflecting mirror to perform nutation scanning before performing iterative adjustment of the driving voltage of the polarization controller, so that the first received optical power value reaches the maximum value; the first received optical power value is the signal optical power value received by the laser communication terminal from the peer laser communication terminal.
[0060] In some embodiments, the main controller 101 is further configured to: according to a preset time-division protocol, enable the laser communication terminal and the peer laser communication terminal to alternately perform polarization state closed-loop adjustment, and allow only one laser communication terminal to actively adjust the driving voltage of its polarization controller at any given time.
[0061] The main controller 101 can be implemented by FPGA, DSP, ASIC, SoC or a combination thereof, and runs control software such as polarization control logic, SPGD algorithm, nutation control logic and time division cooperative protocol on it. It outputs multiple driving voltages to polarization controller 103 through D / A conversion circuit, and receives the received optical power value returned by the other end through A / D sampling or communication interface.
[0062] Figure 4 This is a flowchart of an active polarization switching method for a laser communication terminal according to an embodiment of this disclosure. For ease of explanation, the following detailed description uses the establishment of an inter-satellite laser link between the laser communication terminal of this disclosure (denoted as the first laser communication terminal) and a traditional fixed polarization terminal (denoted as the second laser communication terminal) as an example. It should be understood that this method is also applicable to link establishment scenarios between two laser communication terminals of this disclosure. Figure 4 As shown, the active polarization switching method 400 for a laser communication terminal includes: Step S401: Before establishing the link, the first laser communication terminal acquires the polarization reference state of the second laser communication terminal.
[0063] The first laser communication terminal obtains the polarization reference state of the second laser communication terminal in advance through methods such as ephemeris information, remote uploading from the ground station, inter-satellite network management protocol broadcasting, or terminal information database query. The polarization reference state includes standard A polarization state, standard B polarization state, or any non-standard polarization state.
[0064] Step S402: The main controller sends a polarization state pre-switching command to the polarization controller according to the polarization reference state.
[0065] The main controller of the first laser communication terminal calculates the required driving voltage value for the polarization controller based on the polarization reference state. The main controller internally stores a polarization state-voltage mapping table or function, which records the correspondence between the driving voltage combinations of the polarization controller and the output polarization state. By looking up the table or calculating based on the polarization reference state at the other end, the main controller obtains the driving voltage value required to match the polarization state of the polarization controller output with the polarization reference state, and encodes this voltage value as a polarization state pre-switching command.
[0066] Step S403: The polarization controller changes the polarization state of the transmitted beam in the common optical path of transmission and reception according to the polarization state pre-switching command, so that the polarization state of the transmitted beam matches the polarization reference state.
[0067] The main controller sends the generated polarization state pre-switching command to the polarization controller. Upon receiving the command, the polarization controller applies a corresponding electronic drive signal to its internal polarization state control element based on the drive voltage value contained in the command, switching the polarization state of the emitted beam to a polarization state that the second laser communication terminal can receive, thus satisfying the polarization matching condition. After both sides complete acquisition, an initial bidirectional laser inter-satellite link is established.
[0068] Steps S401 to S403 above constitute the pre-switching mode before link establishment (i.e., the coarse matching stage). This stage does not rely on closed-loop feedback and belongs to open-loop preset control. By acquiring the polarization reference state of the other end in advance and actively adjusting the polarization state of the local end accordingly, both parties can quickly complete the initial acquisition and bidirectional link establishment in the coarse matching state, avoiding the problems of acquisition failure or excessively long link establishment time due to polarization mismatch in traditional schemes.
[0069] After the initial bidirectional link is established, since the coupling efficiency of the spatial light to the receiving fiber is greatly affected by the beam pointing deviation, nutation scanning is required first to optimize the coupling efficiency between the spatial light and the fiber, thereby decoupling the spatial coupling mismatch and polarization state mismatch.
[0070] like Figure 5 As shown, in one embodiment, the active polarization switching method of the laser communication terminal further includes: Step S404: The main controller sends a nutation scan command to the drive module of the precision tracking fast-reflection mirror to control the precision tracking fast-reflection mirror to perform nutation scan.
[0071] Nucleation scanning refers to the main controller applying sinusoidal perturbation signals to the precision tracking fast mirror along two mutually orthogonal axes, causing the reflected beam to trace a tiny circular trajectory in space. The nutation radius is optimized based on the system link budget and the travel range of the precision tracking fast mirror, typically ranging from a few microradians to tens of microradians. The nutation frequency is set according to the bandwidth characteristics of the precision tracking fast mirror, typically ranging from 100Hz to 500Hz.
[0072] Step S405: During the nutation scanning process performed by the precision tracking fast mirror, the first laser communication terminal monitors the first received optical power value in real time.
[0073] The first received optical power value is the signal optical power value received by the first laser communication terminal from the second laser communication terminal. The receiving detection module of the first laser communication terminal continuously detects this optical power value during the nutation scanning process and transmits the detection result to the main controller in real time.
[0074] Step S406: The main controller uses the first received optical power value as an evaluation index to find the fast-reflecting mirror deflection angle that maximizes the first received optical power value.
[0075] The main controller records the relationship between the first received optical power value and the deflection angle of the fine-tracking fast-reflecting mirror during the nutation scanning process. When the optical power reaches its maximum value, the fine-tracking fast-reflecting mirror is locked at that angle position to complete the optimization of the coupling angle between the spatial light and the optical fiber at this end.
[0076] In some embodiments, the second laser communication terminal also performs the nutation scanning process described in steps S404 to S406 above to optimize the spatial coupling efficiency of the signal light received from the first laser communication terminal. After the nutation scanning of both parties is completed, the spatial coupling mismatch loss has been minimized, providing a stable optical signal input for subsequent polarization state closed-loop fine-tuning.
[0077] After the nutation scan is completed, the closed-loop fine-tuning stage of polarization state begins. For example... Figure 6 As shown, in one embodiment, the active polarization switching method of the laser communication terminal further includes: Step S407: The first laser communication terminal receives the second received optical power value. The second received optical power value is the signal optical power value received by the second laser communication terminal from the first laser communication terminal.
[0078] Specifically, the receiving and detection module of the second laser communication terminal detects the signal optical power value received from the first laser communication terminal in real time and transmits this power value back to the first laser communication terminal via the communication link. The transmission methods include, but are not limited to: real-time transmission via digital telemetry through an established inter-satellite laser communication link, or transmission via a satellite-to-ground relay link through a ground station before being uploaded to the first laser communication terminal. The main controller of the first laser communication terminal receives this second received optical power value and uses it as feedback for subsequent closed-loop fine-tuning. This "cross-satellite closed-loop feedback" mechanism allows the polarization optimization target to directly aim at the final performance indicator of "maximum actual received light intensity at the other end," avoiding the deficiency of relying solely on local polarization monitoring and failing to perceive the actual polarization coupling loss of the space link.
[0079] Step S408: The first laser communication terminal uses the received second received optical power value as feedback to iteratively adjust the driving voltage of the polarization controller so that the second received optical power value reaches its maximum value.
[0080] Specifically, the main controller uses the second received optical power value as an evaluation function and employs an iterative optimization algorithm (e.g., Stochastic Parallel Gradient Descent, SPGD) to iteratively update the multi-channel drive voltage of the polarization controller. The core mechanism of the SPGD algorithm is as follows: the main controller applies a random perturbation voltage to each drive channel of the polarization controller, estimates the gradient direction that maximizes the optical power based on the change in the second received optical power value before and after the perturbation, and updates the drive voltage along that direction. This algorithm does not require prior knowledge of the polarization state at the other end, nor does it require modeling the link polarization transmission matrix; it can automatically converge to the optimal coupling point under any polarization substrate. Repeating the above perturbation-measurement-update process, the second received optical power value gradually increases and approaches its maximum value.
[0081] like Figure 7 As shown, in one embodiment, the stochastic parallel gradient descent algorithm includes the following steps: Step S4081: Initialize the driving voltage of the polarization controller and set the disturbance amount and gain coefficient.
[0082] The main controller initializes the four-channel drive voltage of the polarization controller to its initial value. Initial value The polarization reference state can be obtained through a polarization state-voltage mapping table. Simultaneously, the main controller sets the perturbation amount for the SPGD algorithm. (i.e., the amplitude of the random disturbance voltage) and gain coefficient .
[0083] Step S4082: Generate random disturbance voltage.
[0084] In some embodiments, the main controller generates random disturbance voltages. This random perturbation voltage is used to apply a perturbation to the current drive voltage of the polarization controller to detect the effect of voltage changes on the second received optical power value.
[0085] Step S4083: Calculate the positive and negative disturbance voltages based on the random disturbance voltage and the current driving voltage.
[0086] The main controller calculates the positive disturbance voltage V respectively. + and negative disturbance voltage V - :
[0087] Step S4084: Apply the positive perturbation voltage and the negative perturbation voltage to the polarization controller in sequence, and record the first value and the second value of the corresponding second received optical power value respectively.
[0088] The main controller will positively disturb the voltage. The first value is recorded by applying it to the polarization controller and recording the second received optical power value transmitted back from the other end. Subsequently, the main controller applies a negative perturbation voltage to the polarization controller and records the corresponding second received optical power value, which is denoted as the second value. . and This reflects the response of the received optical power at the other end after perturbations in both positive and negative directions are applied at the current driving voltage position.
[0089] Step S4085: Calculate the gradient estimate based on the difference between the first value and the second value.
[0090] The main controller calculates the gradient estimate according to the following formula. . >0 indicates that a positive perturbation increases the optical power, i.e., along the path... Directional movement can increase optical power; <0 indicates that a negative perturbation increases the optical power, i.e., along - Directional movement can increase optical power.
[0091] Step S4086: Update the driving voltage based on the gradient estimate, disturbance, and gain coefficient.
[0092] The main controller updates the drive voltage according to the following formula:
[0093] in, For the updated drive voltage, The current driving voltage, This is the gain coefficient. For the disturbance quantity, This is the gradient estimator.
[0094] Step S4087: Apply the updated driving voltage to the polarization controller and record the corresponding second received optical power value.
[0095] Step S4088: Determine whether the current second received optical power value meets the system preset threshold: if it does, terminate the iteration; otherwise, return to step S4082 and proceed to the next iteration.
[0096] The system's preset threshold can be a combination of any one or more of the following conditions: The change in the current second received optical power value is less than a preset threshold for N consecutive iterations (e.g., the change is less than 1% for 5 consecutive iterations), indicating that the algorithm has converged to near the optimal value; the absolute value of the second received optical power value reaches a preset target value, indicating that the link quality meets the service transmission requirements; or the number of iterations reaches a preset maximum iteration limit to prevent the algorithm from failing to converge and causing an infinite loop in extreme cases. When any of the above conditions are met, the main controller determines that polarization fine-tuning is complete, and the link enters a locked state.
[0097] In one embodiment, the active polarization switching method of the laser communication terminal further includes a time-division coordinated control step: Step S409: The first laser communication terminal and the second laser communication terminal alternately perform polarization state closed-loop adjustment according to the preset time division protocol. At any given time, only one laser communication terminal is allowed to actively adjust the driving voltage of its polarization controller.
[0098] When the first laser communication terminal performs polarization state closed-loop adjustment, the driving voltage of the second laser communication terminal remains unchanged; when the second laser communication terminal performs polarization state closed-loop adjustment, the driving voltage of the first laser communication terminal remains unchanged. Polarization state closed-loop adjustment is performed alternately until the received optical power of both the first and second laser communication terminals meets the system's preset threshold. At this point, polarization state fine-tuning is complete, and the link is locked. Both parties then enter full-duplex data transmission mode.
[0099] This concludes the complete process of the active polarization switching method 400 for laser communication terminals. This method achieves end-to-end polarization adaptive control from pre-establishment to post-establishment through the organic coordination of four stages: coarse matching pre-switching, nutation-based spatial optical coupling angle optimization, SPGD closed-loop fine-tuning based on peer optical power feedback, and time-division collaborative control. This enables the terminal to quickly establish and maintain a high-quality communication link with a peer terminal of any polarization state without ground pre-configuration.
[0100] In one embodiment, this embodiment provides a computer-readable storage medium, such as a non-volatile memory, flash memory, solid-state drive, disk, optical disk, etc., on which a computer program (firmware or software program) is stored. When the computer program is executed by the main controller of the laser communication terminal (e.g., FPGA, DSP, SoC, etc. processor), the main controller controls the terminal to execute the active polarization switching link establishment method disclosed herein, including steps such as polarization state pre-switching before link establishment, link establishment, nutation optimization, SPGD polarization closed-loop fine adjustment, and time-division coordination.
[0101] The active polarization-switching laser communication terminal, method, and storage medium of this application have at least the following beneficial effects: First, a polarization controller is inserted into the shared optical path between the polarization-maintaining fiber circulator and the collimator for transmission and reception. Before link establishment, the main controller sends a polarization state pre-switching command to the polarization controller based on the known polarization reference state of the peer laser communication terminal. This makes the polarization state of the transmitted beam match the polarization reference state of the peer, enabling the laser communication terminal to adaptively match the peer laser communication terminal in standard A state, standard B state, and any non-standard polarization state. This significantly improves the networking flexibility and dynamic reconfiguration capability of the space laser communication network.
[0102] Second, by combining a two-stage polarization control strategy that combines coarse matching pre-switching before link establishment with closed-loop fine-tuning after link establishment, the problem of the two parties being unable to establish an initial link under completely unknown polarization states is solved. Furthermore, the polarization state is converged to the optimal matching point through closed-loop optimization based on feedback of the optical power received at the other end, thus balancing link establishment speed and link margin.
[0103] Third, in the closed-loop fine-tuning, this application uses the actual signal power value received by the laser communication terminal at the other end as the feedback quantity for the closed-loop fine-tuning of the polarization controller, so that the polarization optimization target is directly aligned with the final performance indicator of "maximum actual received light intensity at the other end", avoiding the defect of relying solely on local polarization monitoring and being unable to perceive the actual polarization coupling loss of the space link.
[0104] Fourth, this application adopts the Stochastic Parallel Gradient Descent (SPGD) algorithm as the core optimization algorithm for closed-loop fine-tuning. This algorithm does not require knowing the specific type of polarization state at the other end, nor does it require modeling the polarization transfer matrix of the space optical link. It can automatically converge to the optimal matching point under any polarization basis, and restart the tracking of the new optimal value when the polarization state drifts due to changes in the space environment. This greatly improves the environmental adaptability and on-orbit autonomous operation capability of the terminal.
[0105] This disclosure uses flowcharts to illustrate the operations performed by a system according to embodiments of this disclosure. It should be understood that preceding or following operations are not necessarily performed in exact order. Instead, various steps can be processed in reverse order or simultaneously. Furthermore, other operations may be added to these processes, or one or more steps may be removed from these processes.
[0106] Furthermore, it should be noted that the use of terms such as "first" and "second" to define components is merely for the purpose of distinguishing the corresponding components. Unless otherwise stated, these terms have no special meaning and therefore should not be construed as limiting the scope of protection of this disclosure. In addition, although the terminology used in this disclosure is selected from commonly known and used terms, some terms mentioned in this disclosure may have been chosen by the applicant at his or her judgment, and their detailed meanings are explained in the relevant sections of the description herein. Furthermore, this disclosure should be understood not only by the actual terms used, but also by the meaning implied by each term.
[0107] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the protection scope of the technical solutions of the embodiments of the present invention.
[0108] Those skilled in the art will understand that embodiments of this disclosure can be provided as methods, systems, or computer program products. Therefore, this disclosure can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this disclosure can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.
[0109] Obviously, those skilled in the art can make various modifications and variations to this disclosure without departing from its spirit and scope. Therefore, if such modifications and variations fall within the scope of the claims of this disclosure and their equivalents, this disclosure is also intended to include such modifications and variations.
Claims
1. A laser communication terminal with active polarization switching, characterized in that, include: Main controller, polarization-maintaining fiber circulator, polarization controller and collimator; The polarization-maintaining fiber circulator has a first port, a second port, and a third port. The first port is connected to the transmitter of the main controller, and the third port is connected to the receiver of the main controller. The first end of the polarization controller is connected to the second port of the polarization-maintaining fiber circulator, and the second end of the polarization controller is connected to the collimator. The polarization controller is used to apply a polarization state transformation to the light beam transmitted in the optical path between the polarization-maintaining fiber circulator and the collimator. The light beam includes a transmitted beam and a received beam. The main controller is configured to send a polarization state pre-switching command to the polarization controller before link establishment, based on the polarization reference state of the peer laser communication terminal; the polarization controller changes the polarization state of the emitted beam according to the polarization state pre-switching command, so that the polarization state of the emitted beam matches the polarization reference state.
2. The laser communication terminal as described in claim 1, characterized in that, The main controller is further configured to: after the laser communication terminal establishes a bidirectional link with the peer laser communication terminal, use the second received optical power value as a feedback quantity to iteratively adjust the driving voltage of the polarization controller so that the second received optical power value reaches its maximum value; the second received optical power value is the signal optical power value received by the peer laser communication terminal from the laser communication terminal.
3. The laser communication terminal as described in claim 2, characterized in that, Also includes: The following components are arranged sequentially along the optical path: a forward aiming generator, a tracking communication beam splitter, a fine-tracking fast-reflection mirror, a transceiver telescope, and a coarse-tracking mechanism. The main controller is further configured to: control the fine-tracking fast-reflection mirror to perform nutation scanning before iteratively adjusting the driving voltage of the polarization controller, so that the first received optical power value reaches the maximum value; the first received optical power value is the signal optical power value received by the laser communication terminal from the peer laser communication terminal.
4. The laser communication terminal as described in claim 3, characterized in that, Also includes: A capture and tracking detector is used to connect to the tracking output of the tracking communication beam splitter to receive the optical signal after tracking and splitting and generate a nutation tracking error signal.
5. The laser communication terminal as described in claim 2, characterized in that, The main controller is also configured to iteratively adjust the driving voltage of the polarization controller using a stochastic parallel gradient descent algorithm.
6. The laser communication terminal as described in claim 5, characterized in that, The main controller executes the stochastic parallel gradient descent algorithm, including the following steps: Initialize the driving voltage of the polarization controller, and set the perturbation amount and gain coefficient; The following steps are iteratively executed until the second received optical power value meets the system preset threshold: A random perturbation voltage is generated; a positive perturbation voltage and a negative perturbation voltage are calculated based on the random perturbation voltage and the current driving voltage; the positive perturbation voltage and the negative perturbation voltage are applied to the polarization controller in sequence, and the first and second values of the corresponding second received optical power values are recorded respectively; a gradient estimate is calculated based on the difference between the first and second values; the driving voltage is updated based on the gradient estimate, the perturbation amount, and the gain coefficient; the updated driving voltage is applied to the polarization controller, and the corresponding second received optical power value is recorded.
7. The laser communication terminal as described in claim 2, characterized in that, The main controller is also configured to: according to a preset time-division protocol, cause the laser communication terminal and the peer laser communication terminal to alternately perform polarization state closed-loop adjustment, and allow only one laser communication terminal to actively adjust the driving voltage of its polarization controller at any given time.
8. The laser communication terminal as described in claim 1, characterized in that, The polarization controller is an all-fiber electrically controlled polarization controller.
9. An active polarization switching method for a laser communication terminal, applied to a laser communication terminal including a main controller, a polarization-maintaining fiber circulator, a polarization controller, and a collimator, wherein the polarization controller is disposed in the transmit-receive shared optical path between the polarization-maintaining fiber circulator and the collimator, characterized in that, Includes the following steps: Before establishing the link, obtain the polarization reference state of the laser communication terminal at the other end; Based on the polarization reference state, a polarization state pre-switching command is sent to the polarization controller; The polarization controller changes the polarization state of the transmitted beam in the common optical path of transmission and reception according to the polarization state pre-switching command, so that the polarization state of the transmitted beam matches the polarization reference state.
10. The method as described in claim 9, characterized in that, It also includes the following steps: Establish a bidirectional link with the peer laser communication terminal; Using the second received optical power value as feedback, the driving voltage of the polarization controller is iteratively adjusted so that the second received optical power value reaches its maximum value; the second received optical power value is the signal optical power value received by the peer laser communication terminal from the laser communication terminal.
11. The method as described in claim 10, characterized in that, Before performing iterative adjustments to the drive voltage of the polarization controller, the following steps are also included: The precision tracking mirror is controlled to perform nutation scanning, so that the first received optical power value reaches the maximum value; the first received optical power value is the signal optical power value received by the laser communication terminal from the peer laser communication terminal.
12. The method as described in claim 10, characterized in that, The driving voltage of the polarization controller is iteratively adjusted using a stochastic parallel gradient descent algorithm.
13. The method as described in claim 12, characterized in that, The stochastic parallel gradient descent algorithm includes the following steps: Initialize the driving voltage of the polarization controller, and set the perturbation amount and gain coefficient; The following steps are iteratively executed until the second received optical power value meets the system preset threshold: A random perturbation voltage is generated; a positive perturbation voltage and a negative perturbation voltage are calculated based on the random perturbation voltage and the current driving voltage; the positive perturbation voltage and the negative perturbation voltage are applied to the polarization controller in sequence, and the first and second values of the corresponding second received optical power values are recorded respectively; a gradient estimate is calculated based on the difference between the first and second values; the driving voltage is updated based on the gradient estimate, the perturbation amount, and the gain coefficient; the updated driving voltage is applied to the polarization controller, and the corresponding second received optical power value is recorded.
14. The method as described in claim 10, characterized in that, Also includes: According to the preset time-division protocol, the polarization state closed-loop adjustment is performed alternately with the peer laser communication terminal, and only one laser communication terminal is allowed to actively adjust the driving voltage of its polarization controller at any given time.
15. A computer-readable storage medium, characterized in that, The system stores a computer program, which, when executed by the main controller of the laser communication terminal, causes the laser communication terminal to perform the method as described in any one of claims 9 to 14.