Laser-terahertz multimode inter-satellite communication system and method

Abstract

This invention discloses a laser-terahertz multimode inter-satellite communication system and method. The system includes a laser communication terminal and a terahertz communication terminal, both sharing the same aiming, acquisition, and tracking servo mechanism, arranged coaxially or nearly parallelly. A Tbps-level ultra-high-speed link with a beamwidth of approximately 0.00X degrees is established between laser terminals, while a 100Gbps-level high-speed link with a beamwidth of approximately 0.X degrees is established between terahertz terminals. Utilizing the characteristic that the terahertz beamwidth is 1-2 orders of magnitude wider than that of the laser, the terahertz link can still maintain stable communication when the laser link is interrupted due to extremely narrow beam misalignment. Simultaneously, the system supports various flexible operating modes such as laser single-link, terahertz single-link, primary / backup, parallel, and aggregation, depending on the link status or service requirements. This invention, through structural reuse, effectively reduces the requirements for servo accuracy without significantly increasing satellite costs, greatly improving the reliability and cost-effectiveness of inter-satellite communication.

Description

Technical Field

[0001] This invention relates to the field of inter-satellite wireless communication technology, and in particular to a highly reliable broadband laser-terahertz multimode inter-satellite communication system and method that combines ultra-high-speed laser communication with high-speed terahertz communication and shares a targeting, acquisition, and tracking servo system. Background Technology

[0002] With the rapid growth in demand for applications such as satellite internet, integrated space-ground information networks, distributed remote sensing networks, constellation collaborative computing, and inter-satellite big data backhaul, high-speed inter-satellite communication capabilities have become a key element in improving satellite system performance. Among existing high-speed inter-satellite communication solutions, laser communication has become an important technical route for achieving Tbps-level ultra-high-speed inter-satellite communication due to its advantages such as high bandwidth, high speed, strong resistance to electromagnetic interference, and abundant spectrum resources. However, laser communication typically uses extremely narrow beam transmission, with beam divergence angles reaching approximately 0.00X metric degrees. While it can achieve extremely high directional energy concentration and ultra-high-speed communication, it also places extremely high demands on the pointing, acquisition, and tracking (PAT) accuracy of inter-satellite transceivers. Once real-time tracking deviates due to platform vibration, attitude disturbances, orbital errors, thermal deformation, or servo control errors, the communication link quality may rapidly degrade or even be interrupted, thereby affecting the stability and reliability of high-speed inter-satellite communication.

[0003] In contrast, terahertz communication combines high bandwidth and high directivity, enabling high-speed data transmission at the hundreds of Gbps level. Compared to laser communication, the 3dB beamwidth of terahertz communication antennas typically reaches approximately 0.X metric units, which is 1 to 2 orders of magnitude wider than laser beamwidth. This means that under the same inter-satellite pointing conditions, terahertz links have stronger fault tolerance for real-time alignment errors at the terminal, significantly reducing the stringent requirements on the control precision of servo mechanical systems.

[0004] However, in existing technologies, laser links and terahertz links are usually designed independently, which leads to problems such as redundant equipment configuration, high system complexity, large onboard resource consumption, and high cost, making it difficult to simultaneously meet the comprehensive requirements of ultra-high speed, low cost, and high reliability for inter-satellite communication. Therefore, there is an urgent need to propose a new technical solution that, while inheriting the existing laser inter-satellite communication system architecture as much as possible, introduces low-cost terahertz high-speed communication capabilities and achieves highly reliable, multi-mode, and broadband inter-satellite communication through structural reuse and link collaboration. Summary of the Invention

[0005] Purpose of the invention: The purpose of this invention is to provide a laser-terahertz multimode inter-satellite communication system and method to solve the problems of existing inter-satellite laser communication systems, such as excessively narrow beams requiring high precision from the servo system, links being easily interrupted due to tracking errors, insufficient system reliability, and high cost of repetitive configuration of multiple independent terminals.

[0006] Technical solution: To achieve the above objectives, the present invention adopts the following technical solution.

[0007] This invention provides a laser-terahertz multimode inter-satellite communication system, including communication satellite A and communication satellite B; communication satellite A is equipped with a first aiming, acquisition and tracking servo mechanism, a first laser communication terminal and a first terahertz communication terminal; communication satellite B is equipped with a second aiming, acquisition and tracking servo mechanism, a second laser communication terminal and a second terahertz communication terminal.

[0008] The first aiming, acquisition, and tracking servo mechanism has a first pointing platform, on which the first laser communication terminal and the first terahertz communication terminal are mounted; the second aiming, acquisition, and tracking servo mechanism has a second pointing platform, on which the second laser communication terminal and the second terahertz communication terminal are mounted. The first aiming, acquisition, and tracking servo mechanism drives the first pointing platform to cause the first laser communication terminal and the first terahertz communication terminal to jointly point, acquire, and track communication satellite B; the second aiming, acquisition, and tracking servo mechanism drives the second pointing platform to cause the second laser communication terminal and the second terahertz communication terminal to jointly point, acquire, and track communication satellite A.

[0009] An ultra-narrow beam laser communication link is established between the first laser communication terminal and the second laser communication terminal, providing Tbps-level high-speed data transmission; a terahertz communication link with a wider beam than the laser communication link is established between the first terahertz communication terminal and the second terahertz communication terminal, providing hundreds of Gbps-level high-speed data transmission. Furthermore, the terahertz communication link and the laser communication link share the first and second aiming, acquisition, and tracking servo mechanisms.

[0010] In this scheme, the first laser communication terminal and the first terahertz communication terminal are installed on the same servo pointing platform, using either a coaxial arrangement or a near-parallel axis arrangement; the second laser communication terminal and the second terahertz communication terminal are installed with corresponding structures. For the near-parallel axis arrangement, due to the installation distance between the laser terminal and the terahertz terminal on the pointing platform, there is a fixed deviation in the point where their beams point towards the target satellite. This deviation is compensated for by presetting an offset angle during installation or by introducing electronically controlled phase-shift scanning inside the terminal, ensuring that both links can fall within the acquisition field of view of the other terminal.

[0011] The 3dB beamwidth of the laser communication link is 0.001 to 0.009 degrees, and the 3dB beamwidth of the terahertz communication link is 0.01 to 0.09 degrees. The beamwidth of the terahertz communication link is 1 to 2 orders of magnitude higher than that of the laser communication link, and its beam coverage is greater than that of the laser communication terminal. In this embodiment, the typical pointing error of the servo system is ±0.05 degrees, and the 3dB beamwidth of the terahertz link is 0.2 degrees, which is greater than twice the pointing error. Therefore, under the same servo tracking conditions, the terahertz link can maintain stable communication, thereby effectively reducing the system's requirements for real-time alignment accuracy. When the laser link experiences performance degradation or interruption due to tracking misalignment caused by its ultra-narrow beam, the terahertz link can maintain stable communication with its wider beam, thus ensuring the continuity of inter-satellite data transmission. At the same time, the terahertz link reuses the original servo tracking system of the laser link, eliminating the need for a separate high-precision independent servo mechanism.

[0012] The system of this invention also includes a link management and switching control module, used to acquire link status parameters and, based on the link status parameters of the laser communication link and the terahertz communication link, switch between laser single-link communication mode, terahertz single-link communication mode, laser-primary terahertz backup communication mode, and laser and terahertz parallel communication or link aggregation mode; and when the laser communication link is detected to have stabilized, at least some services will be switched back from the terahertz communication link to the laser communication link. The laser communication link is used to carry Tbps-level main data streams, and the terahertz communication link is used to carry at least one of the following: hundreds of Gbps-level data streams, control data streams, low-latency critical data streams, continuous service data streams during laser link misalignment, or backup data streams.

[0013] The link management and switching control module is integrated into the satellite platform's onboard computer or implemented by a separate FPGA control unit. It is connected to the laser communication terminal and terahertz communication terminal via the satellite's internal bus to obtain link status information and issue switching commands.

[0014] A control information exchange link is also provided between communication satellite A and communication satellite B for transmitting directional control information, link status information, acquisition synchronization information, or mode switching commands. This control information exchange link is multiplexed into the auxiliary overhead channel of the terahertz communication link, or implemented through a separate low-rate radio frequency link.

[0015] The present invention also provides a laser-terahertz multimode inter-satellite communication method based on the above system, which specifically includes the following steps:

[0016] Step 1: Drive the first pointing platform through the first aiming, capturing and tracking servo mechanism, so that the first laser communication terminal and the first terahertz communication terminal are both pointing toward communication satellite B; and drive the second pointing platform through the second aiming, capturing and tracking servo mechanism, so that the second laser communication terminal and the second terahertz communication terminal are both pointing toward communication satellite A, thereby completing the mutual pointing, capturing and tracking of each terminal on the two satellites;

[0017] Step 2: Establish laser communication links and terahertz communication links, with the beamwidth of the terahertz communication link being greater than that of the laser communication link; simultaneously, based on the current inter-satellite data link requirements or system energy consumption requirements, select one of the following as the initial working mode to perform link establishment: laser single-link communication mode, terahertz single-link communication mode, laser and terahertz parallel communication mode, or laser-dominant terahertz backup communication mode.

[0018] Step 3: Monitor the link status parameters of the laser communication link and the terahertz communication link in real time. The link status parameters include at least one of the following: received power, signal-to-noise ratio, bit error rate, and tracking error.

[0019] Step 4: When the received power of the laser communication link is detected to be lower than the preset threshold or the link is interrupted, based on the wider beam characteristics of the terahertz communication link, the communication service is switched to the terahertz communication link to maintain data transmission. When switching to the terahertz communication link, the terahertz communication link carries at least one of the following: a 100 Gbps-level data stream, a control data stream, a low-latency critical data stream, or a backup data stream.

[0020] Step 5: Continue to monitor the link status of the laser communication link. When it recovers to above the preset threshold, switch the communication service from the terahertz communication link back to the laser communication link, or switch to the dual-link parallel transmission state.

[0021] Beneficial effects: Compared with the prior art, the present invention has at least the following beneficial effects:

[0022] (1) When the laser link is misaligned or interrupted, the terahertz link can still maintain high-speed communication at hundreds of Gbps, avoiding the failure of the entire link.

[0023] (2) Since the beamwidth of the terahertz link is significantly larger than that of the laser link, the system’s tolerance to pointing error can be improved, and the burden on the real-time high-precision mechanical servo system can be reduced.

[0024] (3) The terahertz terminal can reuse the aiming, acquisition and tracking mechanism of the original laser terminal without the need to add an additional high-precision pointing platform.

[0025] (4) Depending on the business scenario, you can choose between laser ultra-high speed link, terahertz low-cost high speed link or a combination of both.

[0026] (5) Under the condition of limited onboard resources, achieve higher reliability, higher availability and more flexible broadband inter-satellite communication capabilities. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings are briefly described below. It should be understood that the following drawings only show some embodiments of the present invention and do not limit the scope of protection of the present invention.

[0028] Figure 1 This is a block diagram illustrating the principle of the high-reliability broadband laser-terahertz multimode inter-satellite communication system of the present invention.

[0029] Data stream 1 is formed between the first laser communication terminal and the second laser communication terminal, with a communication rate of Tbps; data stream 2 is formed between the first terahertz communication terminal and the second terahertz communication terminal, with a communication rate of hundreds of Gbps; the laser link beamwidth is approximately 0.00X degrees, and the terahertz link beamwidth is approximately 0.X degrees.

[0030] Figure 2 This is a schematic diagram of a high-reliability inter-satellite link.

[0031] Figure 3 This is a schematic diagram of laser-terahertz multimode operation.

[0032] Figure 4 The diagram shows a shared servo mechanism for laser and terahertz systems. (a) is a schematic diagram of the coaxial arrangement structure and its front view; (b) is a schematic diagram of the near-parallel axis arrangement structure and its front view; and (c) is a schematic diagram of the relationship between structure reuse and pointing accuracy. Detailed Implementation

[0033] The technical solution of the present invention will be further described below with reference to the embodiments and accompanying drawings. It should be understood that the following embodiments are only used to illustrate the present invention and are not intended to limit the scope of protection of the present invention; without departing from the concept of the present invention, the laser link, terahertz (radio frequency) link and mode switching strategy can be adjusted according to the actual system requirements.

[0034] Example 1: System Structure Example

[0035] like Figure 1 As shown, this embodiment provides a laser-terahertz multimode inter-satellite communication system for inter-satellite data transmission between two communication satellites.

[0036] Communication satellite A is located at one end of the link, and communication satellite B is located at the other end of the link. Communication satellite A is equipped with a first aiming, acquisition, and tracking servo mechanism, a first laser communication terminal, and a first terahertz communication terminal; communication satellite B is equipped with a second aiming, acquisition, and tracking servo mechanism, a second laser communication terminal, and a second terahertz communication terminal.

[0037] The first aiming, acquisition, and tracking servo mechanism has a first pointing platform, on which the first laser communication terminal and the first terahertz communication terminal are mounted. The second aiming, acquisition, and tracking servo mechanism has a second pointing platform, on which the second laser communication terminal and the second terahertz communication terminal are mounted. The first aiming, acquisition, and tracking servo mechanism drives the first pointing platform to cause the first laser communication terminal and the first terahertz communication terminal to jointly point, acquire, and track communication satellite B. The second aiming, acquisition, and tracking servo mechanism drives the second pointing platform to cause the second laser communication terminal and the second terahertz communication terminal to jointly point, acquire, and track communication satellite A. In other words, the laser communication link and the terahertz communication link share the same aiming, acquisition, and tracking servo system.

[0038] In this physical structure, the first laser communication terminal and the first terahertz communication terminal are arranged coaxially or nearly parallel on the first pointing platform, specifically as follows: Figure 4 As shown in (a) (coaxial arrangement) and Figure 4 As shown in (b) (near parallel axis arrangement); the second laser communication terminal and the second terahertz communication terminal are installed on the second pointing platform using a corresponding structure. Figure 4 Figure (c) illustrates the logical relationship in this structure reuse configuration: the laser terminal acts as the primary pointing terminal, providing high-precision coarse pointing, while the terahertz terminal, acting as the secondary terminal, utilizes its wide beam and insensitivity to minor deviations to establish a stable link. For the near-parallel axis arrangement, due to the installation distance between the laser and terahertz terminals on the pointing platform, there is a fixed deviation in the point where their beams point onto the target satellite. This deviation is compensated for by presetting an offset angle during installation or by introducing electronically controlled phase-shift scanning within the terminals, ensuring that both links fall within the acquisition field of view of the other terminal.

[0039] A laser communication link is established between the first laser communication terminal and the second laser communication terminal. The 3dB beamwidth of this laser communication link is 0.001 degrees to 0.009 degrees, which can be used to transmit Tbps-level ultra-high-speed data streams.

[0040] A terahertz communication link is established between the first and second terahertz communication terminals. The 3dB beamwidth of this terahertz communication link is 0.01 to 0.09 degrees, wider than that of a laser link, thus providing higher tolerance for pointing errors and enabling high-speed data streams at hundreds of Gbps. In this embodiment, the typical pointing error of the servo system is ±0.05 degrees, and the terahertz 3dB beamwidth is 0.2 degrees, greater than twice the pointing error. Therefore, under the same servo tracking conditions, the terahertz link can maintain stable communication. Since the beam coverage of the terahertz communication terminal is much larger than that of the laser communication terminal, the real-time alignment accuracy requirements of the shared servo system are effectively reduced.

[0041] The system also includes a link management and switching control module, which is integrated into the satellite platform's onboard computer or implemented by a separate FPGA control unit. This module connects to the laser communication terminal and the terahertz communication terminal via the satellite's internal bus to acquire link status information and issue switching commands. A control information exchange link established between communication satellite A and communication satellite B is specifically used to transmit directional control information, link status information, acquisition synchronization information, and mode switching commands, ensuring coordinated closed-loop control among the system's modules. This control information exchange link is multiplexed into the auxiliary overhead channel of the terahertz communication link or implemented through a separate low-rate radio frequency link.

[0042] Example 2: Reliability Enhancement Example

[0043] like Figure 2 As shown, during high-speed inter-satellite communication, if the laser link deviates from its real-time tracking due to factors such as relative attitude changes between the two satellites, platform micro-vibrations, or elastic deformation caused by temperature changes, the link receiving power will decrease rapidly due to the extremely narrow laser beam, and in severe cases, the link will be interrupted.

[0044] In this embodiment, because the beamwidth of the terahertz link is much larger than that of the laser link, under the same servo tracking error conditions, the terahertz link is usually still within the effective coverage range and can still maintain stable communication at the 100Gbps level. Specifically, when the servo pointing error is ±0.05 degrees, for a laser link with a 3dB beamwidth of 0.005 degrees, the pointing deviation has far exceeded its beamwidth, and the link will be completely interrupted; while for a terahertz link with a 3dB beamwidth of 0.2 degrees, the pointing deviation is still within its 3dB beamwidth range, and the link quality remains good. At this time, the link management and switching control module switches all or part of the service data originally carried by the laser link to the terahertz link to ensure that the service is not interrupted.

[0045] Once the laser link has been precisely aligned and returned to normal receiving power and bit error rate range, the link management and switching control module detects that the laser communication link has stabilized and switches at least some services from the terahertz communication link back to the laser communication link, or maintains the parallel transmission of laser and terahertz dual links to meet the service requirements of high speed and low latency.

[0046] Example 3: Multi-mode working example

[0047] like Figure 3 As shown, the system of the present invention supports multiple working modes, including but not limited to:

[0048] Laser Single-Link Mode: When the servo system is in good condition and the link is precisely aligned, only the laser link is activated to achieve Tbps-level ultra-high-speed transmission.

[0049] Terahertz single-link mode: When the service rate requirement is lower than Tbps, or when considering reducing system energy consumption, reducing terminal burden, and reducing costs, only the terahertz link is enabled to achieve high-speed transmission at the level of hundreds of Gbps.

[0050] Laser-primary, terahertz-backup mode: The laser link serves as the primary bearer link, while the terahertz link acts as a backup link, automatically taking over services when the laser link fails. The terahertz link can be used to carry data streams at speeds of hundreds of Gbps, control data streams, low-latency critical data streams, or continuous service data streams during laser link outages.

[0051] Laser and terahertz parallel communication mode: Laser links and terahertz links transmit different types of data simultaneously. For example, the laser link carries high-capacity payload data, while the terahertz link carries control information, low-latency data, or backup data.

[0052] Link aggregation mode: Laser links and terahertz links are used together for data transmission with higher total throughput. This means the same data stream is split and transmitted in parallel through two links, then reassembled at the receiving end to meet the needs of inter-satellite broadband services. In this mode, the link management and switching control module is responsible for the distribution and reassembly of the data stream, dynamically adjusting the data allocation ratio based on the real-time rates and capabilities of the two links.

[0053] The system can select one of the above modes as the initial working mode to establish the link, based on the current inter-satellite data link requirements or system energy consumption requirements.

[0054] Example 4: Structural Reuse Example

[0055] like Figure 4As shown, the laser communication terminal and the terahertz communication terminal are mounted on the same pointing platform, arranged coaxially or nearly parallel to each other. This allows the attitude adjustment output by the servo mechanism to simultaneously affect both the laser and terahertz terminals, avoiding the need to design a separate complex servo system for the terahertz terminal. The first laser communication terminal can serve as a high-precision master pointing terminal, while the first terahertz communication terminal shares the coarse pointing results based on it. Because the terahertz beam is wider and less sensitive to minute deviations, stable link establishment can be achieved without significantly increasing the additional pointing accuracy requirements.

[0056] For the coaxial arrangement scheme, the optical center and radio frequency center of the laser terminal and the terahertz terminal coincide, and their beam directions are completely consistent, making control the simplest.

[0057] For a near-parallel axis arrangement, there is an installation gap between the laser terminal and the terahertz terminal on the pointing platform. Let this gap be d, and the inter-satellite distance be L, then the deviation angle of the landing points of the two beams on the target satellite is approximately... When the deviation angle is greater than the terahertz beamwidth, compensation is required. Compensation methods include, but are not limited to: preset the offset angle during installation to make the two beams intersect at the target distance; or introducing electronically controlled phase-shift scanning inside the terahertz terminal to electronically adjust the beam pointing and eliminate fixed deviations. Through the above compensation, it is ensured that both links can establish stable communication.

[0058] Example 5: Communication Method Example

[0059] The present invention also provides a laser-terahertz multimode inter-satellite communication method based on the above system, which specifically includes the following steps:

[0060] Step S1: The first aiming, acquisition and tracking servo mechanism and the second aiming, acquisition and tracking servo mechanism drive the laser communication terminal and the terahertz communication terminal on communication satellite A and communication satellite B respectively to complete the initial pointing, acquisition and tracking between them.

[0061] Step S2: Based on the initial pointing result, establish a laser communication link and a terahertz communication link between communication satellite A and communication satellite B. The laser communication link is an ultra-narrow beam link with a first 3dB beamwidth of 0.001° to 0.009°. The terahertz communication link is a link with a second 3dB beamwidth of 0.01° to 0.09°, and the second 3dB beamwidth is greater than the first 3dB beamwidth. Simultaneously, based on the current inter-satellite data link requirements or system energy consumption requirements, select one of the following as the initial working mode to perform link establishment: laser single-link communication mode, terahertz single-link communication mode, laser and terahertz parallel communication mode, or laser-dominant terahertz backup communication mode.

[0062] Step S3: Monitor the link status parameters of the laser communication link and the terahertz communication link in real time. The link status parameters include at least one of the following: received power, signal-to-noise ratio, bit error rate, and tracking error.

[0063] Step S4: When the link status parameters of the laser communication link are detected to be lower than a preset threshold (e.g., received power lower than a preset threshold, pointing error exceeding a preset threshold) or a link interruption occurs, based on the physical characteristic that the beamwidth of the terahertz communication link is greater than that of the laser communication link, the communication service is switched from the laser communication link to the terahertz communication link, and inter-satellite data transmission is maintained through the terahertz communication link. During the switch to the terahertz communication link, the terahertz communication link is used to carry at least one of the following: 100 Gbps-level data streams, control data streams, low-latency critical data streams, or backup data streams. The preset threshold is determined according to system design specifications; for example, switching is triggered when the received power is lower than the nominal value by 3 dB or the pointing error exceeds half the 3 dB beamwidth of the laser.

[0064] Step S5: After switching the communication service to the terahertz communication link, continue to monitor the link status parameters of the laser communication link in real time.

[0065] Step S6: When the link status parameters of the laser communication link are detected to recover to above the preset threshold (i.e., the laser link stabilizes again), the communication service is switched from the terahertz communication link back to the laser communication link, or switched to a state where the laser communication link and the terahertz communication link are transmitted in parallel.

[0066] Description of alternative implementation methods

[0067] This invention is not limited to the single link structure between the two satellites mentioned above, but can also be applied to the establishment of links between any adjacent satellite nodes in a constellation network composed of multiple satellites.

[0068] The specific rates, operating frequency bands, modulation methods, antenna types, terminal installation methods, control algorithms, and link switching strategies of laser links and terahertz links can all be adjusted according to actual application needs.

[0069] The terms "Tbps level," "hundreds of Gbps level," "0.00X degree," and "0.X degree" used in this document are illustrative and should not be construed as strictly limiting the scope of protection of this invention. "0.00X degree" represents a range from 0.001 degree to 0.009 degree, and "0.X degree" represents a range from 0.01 degree to 0.09 degree.

[0070] The switching triggering conditions are not limited to the received power being lower than a preset threshold. They can also be triggered by a single or combined condition such as deterioration of signal-to-noise ratio, increase in bit error rate, or exceeding the tracking error limit. The specific threshold can be flexibly set according to the system link budget and bit error performance requirements.

Claims

1. A laser-terahertz multimode inter-satellite communication system, characterized in that, include: Communication satellite A and communication satellite B; The first aiming, acquisition and tracking servo mechanism, the first laser communication terminal and the first terahertz communication terminal are installed on communication satellite A; The second aiming, acquisition and tracking servo mechanism, the second laser communication terminal and the second terahertz communication terminal are installed on communication satellite B; The first aiming, capturing, and tracking servo mechanism has a first pointing platform, and the first laser communication terminal and the first terahertz communication terminal are mounted on the first pointing platform; the second aiming, capturing, and tracking servo mechanism has a second pointing platform, and the second laser communication terminal and the second terahertz communication terminal are mounted on the second pointing platform. The first aiming, acquisition, and tracking servo mechanism is used to drive the first pointing platform, so as to drive the first laser communication terminal and the first terahertz communication terminal to point, acquire, and track the communication satellite B together; The second aiming, acquisition, and tracking servo mechanism is used to drive the second pointing platform, so as to drive the second laser communication terminal and the second terahertz communication terminal to point, acquire, and track the communication satellite A together; A laser communication link is established between the first laser communication terminal and the second laser communication terminal to provide Tbps-level high-speed data transmission; A terahertz communication link is established between the first terahertz communication terminal and the second terahertz communication terminal to provide high-speed data transmission at the level of hundreds of Gbps; The terahertz communication link and the laser communication link share the first aiming, acquisition, and tracking servo mechanism and the second aiming, acquisition, and tracking servo mechanism, and the beamwidth of the terahertz communication link is greater than that of the laser communication link; the system also includes a link management and switching control module, which is used to acquire link status parameters and, when it is detected that the laser communication link experiences a decline in link quality or is interrupted due to ultra-narrow beam misalignment, controls the communication service to automatically switch to the terahertz communication link.

2. The system according to claim 1, characterized in that, The 3dB beamwidth of the laser communication link is 0.001 degrees to 0.009 degrees, and the 3dB beamwidth of the terahertz communication link is 0.01 degrees to 0.09 degrees. The beamwidth of the terahertz communication link is 1 to 2 orders of magnitude higher than that of the laser communication link.

3. The system according to claim 1 or 2, characterized in that, The first laser communication terminal and the first terahertz communication terminal are arranged coaxially or nearly parallel on the first pointing platform; the second laser communication terminal and the second terahertz communication terminal are arranged on the second pointing platform in the same way as the first laser communication terminal and the first terahertz communication terminal.

4. The system according to claim 1, characterized in that, The link management and switching control module is used to switch between laser single-link mode, terahertz single-link mode, laser primary terahertz backup mode, and laser and terahertz parallel communication or link aggregation mode according to the link status parameters; and when the laser communication link is detected to have stabilized, at least some services will be switched from the terahertz communication link back to the laser communication link.

5. The system according to claim 1, characterized in that, The laser communication link is used to carry Tbps-level main data streams, and the terahertz communication link is used to carry hundreds of Gbps-level data streams, control data streams, low-latency critical data streams, or continuous service data streams during laser link misalignment.

6. The system according to claim 1, characterized in that, The beam coverage range of the terahertz communication terminal is greater than that of the laser communication terminal, thereby reducing the real-time alignment accuracy requirements of the shared servo system.

7. The system according to claim 1, characterized in that, A control information exchange link is also provided between communication satellite A and communication satellite B, which is used to transmit pointing control information, link status information, acquisition synchronization information or mode switching instructions.

8. A communication method based on the laser-terahertz multimode inter-satellite communication system according to any one of claims 1 to 7, characterized in that, Includes the following steps: The first aiming, capturing, and tracking servo drives the first pointing platform, causing the first laser communication terminal and the first terahertz communication terminal to jointly face the communication satellite B. The second aiming, capturing, and tracking servo drives the second pointing platform, causing the second laser communication terminal and the second terahertz communication terminal to jointly face the communication satellite A, thus completing the mutual pointing, capturing, and tracking of the terminals on the two satellites. Establish laser communication links and terahertz communication links, with the beamwidth of the terahertz communication link being greater than that of the laser communication link; Real-time monitoring of link status parameters of laser communication links and terahertz communication links; When the received power of the laser communication link is detected to be lower than a preset threshold or the link is interrupted, the communication service is switched to the terahertz communication link to maintain data transmission, based on the wider beam characteristics of the terahertz communication link. When switching to the terahertz communication link, the terahertz communication link carries at least one of the following: a 100 Gbps-level data stream, a control data stream, a low-latency critical data stream, or a backup data stream. Continue to monitor the link status of the laser communication link. When it recovers to above the preset threshold, switch the communication service from the terahertz communication link back to the laser communication link, or switch to the dual-link parallel transmission state.

9. The communication method according to claim 8, characterized in that, Based on the current inter-satellite data link requirements or system energy consumption requirements, select one of the following as the initial working mode to establish the link: laser single-link communication mode, terahertz single-link communication mode, laser and terahertz parallel communication mode, or laser-dominant terahertz backup communication mode.

10. The communication method according to claim 8, characterized in that, The link state parameters include at least one of received power, signal-to-noise ratio, bit error rate, and tracking error.

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