Laser communication terminal based on ultra-compact wave combining laser

Abstract

The invention provides a laser communication terminal based on an ultra-compact wave combining laser. The laser communication terminal comprises a wave combining laser module, an optical antenna module, a light splitting module, a beacon receiving module and a signal receiving module. The wave combining laser module is used for combining laser beams with different wavelengths into a main laser beam through a space path. The optical antenna module is used for expanding and collimating the main laser beam, then emitting the main laser beam, and receiving an external incident laser beam. And the light splitting module is used for carrying out polarization state and wavelength separation on the main laser beam and an external incident laser beam, guiding the main laser beam to the optical antenna module, and respectively guiding the external incident laser beam to the beacon receiving module and the signal receiving module. The beacon receiving module is used for acquiring position information, and the signal receiving module is used for acquiring communication information. According to the invention, the laser communication terminal structure with integrated emission and reception, miniaturization and high precision is realized, and the laser communication terminal structure is suitable for free space optical communication and other application scenes.

Description

Technical Field

[0001] This invention relates to the field of optical communication technology, and in particular to a laser communication terminal based on an ultra-compact laser multiplexer. Background Technology

[0002] Laser communication, a communication method that uses laser beams as carriers to transmit information, has been widely used in modern communication fields due to its numerous advantages, such as high bandwidth, strong anti-interference capability, and good confidentiality. It plays an irreplaceable and crucial role, especially in scenarios such as satellite communication and deep space exploration communication. However, in these applications, laser communication systems face the critical challenges of size and weight limitations.

[0003] Satellites typically have very limited payload space, severely restricting the size and weight of equipment. This necessitates that laser communication equipment be as miniaturized and lightweight as possible. Laser communication systems usually separate beacon lasers and signal lasers, each equipped with its own independent optical path system, drive circuitry, and heat dissipation device. This results in a complex, bulky, and heavy system structure, severely limiting the further development and application of laser communication systems in applications such as satellites where size and weight are extremely critical. Summary of the Invention

[0004] In view of this, the purpose of this invention is to provide a laser communication terminal based on an ultra-compact laser combiner to solve the above-mentioned technical problems.

[0005] To achieve the above objectives, the present invention provides a laser communication terminal based on an ultra-compact laser multiplexer, comprising: A laser combining module is used to combine laser beams of different wavelengths into a single main laser beam through a spatial path. An optical antenna module is used to expand, collimate, and emit the main laser beam to be emitted, as well as to receive externally incident laser beams. The beam splitter module is used to separate the polarization state and wavelength of the main laser beam from the externally incident laser beam, guide the main laser beam to the optical antenna module, and guide the externally incident laser beam to the beacon receiving module and the signal receiving module respectively. The beacon receiving module is used to receive and process the beacon light signal used for position information acquisition in the externally incident laser beam, and output the corresponding position information; The signal receiving module is used to receive and process the optical signal carrying communication information in the externally incident laser beam, and output the corresponding electrical signal.

[0006] In a further technical solution, the laser combining module includes: a beacon emitting laser for emitting a beacon laser beam of a first wavelength; a signal emitting laser for emitting a signal laser beam of a second wavelength; a first beam shaping mirror for collimating and shaping the first wavelength beacon laser beam; a second beam shaping mirror for collimating and shaping the second wavelength signal laser beam; a reflector for reflecting the shaped first wavelength beacon laser beam to a first dichroic mirror to combine it with the second wavelength signal laser beam; and a first dichroic mirror for merging the shaped first wavelength beacon laser beam and the shaped second wavelength signal laser beam into a single main laser beam.

[0007] In a further technical solution, the optical antenna module includes a primary mirror, a secondary mirror, and a fast reflector. When receiving an externally incident beacon laser beam or signal laser beam, the primary mirror reflects the beacon laser beam or signal laser beam to the secondary mirror, and the secondary mirror further reflects the beacon laser beam or signal laser beam to the fast reflector. When emitting a main laser beam, the fast reflector guides the main laser beam to the secondary mirror, the secondary mirror reflects the main laser beam back to the primary mirror, and the primary mirror expands and collimates the laser beam before it is emitted into free space.

[0008] In a further technical solution, the beam splitting module includes a quarter-wave plate, a polarizing beam splitter, and a second dichroic mirror; The polarizing beam splitter is used to reflect the main laser beam to the quarter-wave plate, and the quarter-wave plate is used to transmit the main laser beam and allow it to enter the optical antenna module via the fast reflector. The quarter-wave plate and the polarizing beam splitter are used to sequentially transmit the beacon laser beam to be received, and the second dichroic mirror is used to reflect the beacon laser beam to be received to the beacon receiving module. The quarter-wave plate, the polarizing beam splitter, and the second dichroic mirror are used to sequentially transmit the signal light to be received, so that the signal laser beam to be received enters the signal receiving module.

[0009] In a further technical solution, the beacon receiving module includes a narrowband filter, a first focusing lens, and a CMOS beacon detector. The narrowband filter is used to filter out stray light of non-target wavelengths. The first focusing lens is used to focus the received beacon laser beam of the first wavelength onto the CMOS beacon detector. The CMOS beacon detector is used to image the light spot formed on the detector surface by the focused beacon laser beam and output the position information of the light spot.

[0010] In a further technical solution, the signal receiving module includes a narrowband filter, a second focusing lens, and an APD detector. The filter is used to filter out background stray light, the second focusing lens is used to focus the signal laser beam onto the APD detector, and the APD detector is used to receive the signal laser beam and convert the signal laser beam into an electrical signal.

[0011] In a further technical solution, the emission wavelength of the beacon emitting laser is 808nm, and the emission wavelength of the signal emitting laser is 1540nm; the reflector is disposed between the beacon emitting laser and the first dichroic mirror to guide the 808nm laser to the first dichroic mirror; A first beam shaping mirror is disposed between the beacon emitting laser and the reflector; a second beam shaping mirror is disposed between the signal emitting laser and the first dichroic mirror.

[0012] In a further technical solution, the first dichroic mirror reflects 808nm wavelength light and transmits 1540nm wavelength light; the primary mirror is a concave parabolic reflector, the secondary mirror is a convex parabolic reflector, and the optical antenna module has a magnification of 5-10 times; the fast reflector is obliquely mounted behind the secondary mirror to change the beam direction and adjust the emission direction to achieve target tracking.

[0013] In a further technical solution, the quarter-wave plate is disposed between the fast-reflecting mirror and the polarizing beam splitter to realize the conversion between linearly polarized light and circularly polarized light; The polarizing beam splitter is installed at an angle, which can reflect S-polarized light and transmit P-polarized light; The second dichroic mirror is used to reflect the 808nm beacon laser beam to the beacon receiving module and transmit the 1540nm communication laser beam to the signal receiving module; The first narrowband filter has a center wavelength of 808nm and a bandwidth of ±2nm; The second narrowband filter has a center wavelength of 1563nm and a bandwidth of ±2nm.

[0014] In a further technical solution, the first and second focusing lenses adopt a multi-piece structure; The primary mirror is parallel to the optical axis of the secondary mirror but is arranged off-axis; The fast reflector, the quarter-wave plate, the polarizing beam splitter, and the second dichroic mirror are arranged coaxially.

[0015] The above technical solution has the following beneficial effects: This invention proposes a laser communication terminal based on an ultra-compact laser multiplexer. Through chip integration technology and optimized optical path design, the beacon laser and signal laser are integrated into a highly integrated laser multiplexer module. This integrated design greatly simplifies the traditional complex optical path structure, reducing unnecessary optical components and connecting parts. Furthermore, due to the reduction in optical components, the overall system weight is significantly reduced compared to traditional discrete designs.

[0016] To achieve miniaturization and structural integration of laser communication terminals, this invention integrates a beacon laser and a signal laser into a single laser combining module. The beacon laser emits 808nm beacon light for location information acquisition, while the signal laser emits 1540nm communication signal light. Both are arranged parallel to each other within the module. Through the strategic placement of optical elements such as a first beam shaper, a second beam shaper, a reflector, and a dichroic mirror, the two laser beams are shaped and coupled along their spatial paths, ultimately combining into a single main laser beam for output. This integration allows the beacon and signal lights to share a downstream optical path, saving space, simplifying the optical path structure, and facilitating overall module packaging and stability control. This effectively meets the engineering requirements of laser communication systems for compact size, streamlined structure, and high integration.

[0017] To meet the requirements of miniaturization and common-path design in laser communication terminals, this invention proposes a method for combining and splitting multiple wavelengths of light, and constructs a compact and efficient optical path layout. In the transmission path, a dichroic mirror is used to combine two laser beams of different wavelengths (808nm and 1540nm) into a coaxial main laser beam. This beam is then guided into the optical antenna module for beam expansion and transmission via polarization control devices such as a polarization beam splitter and a quarter-wave plate. In the receiving path, the external laser signal returns via the optical antenna module and propagates in the reverse direction along the original transmission path. Under the double-pass transmission effect of the quarter-wave plate, its polarization state is changed and it passes through the polarization beam splitter, thus separating it from the transmission path. Subsequently, a dichroic mirror is used to separate different wavelengths in the incident light: the 808nm beacon light is reflected to the beacon receiving module, and the 1563nm communication light is transmitted to the signal receiving module, achieving wavelength splitting in the receiving path. The aforementioned beam combining and beam splitting mechanisms, combined with polarization state control and wavelength selection, construct a compact optical system with a common optical path but separate functions, ensuring that the system has high efficiency and miniaturization characteristics, making it suitable for space-constrained laser communication applications. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of the structure of a laser communication terminal based on an ultra-compact laser multiplexer according to an embodiment of the present invention.

[0020] Explanation of icon numbers: 001, Beacon emitting laser; 002, Signal emitting laser; 003, First beam shaping mirror; 004, Second beam shaping mirror; 005, Reflector; 006, First dichroic mirror; 007, Primary mirror; 008, Secondary mirror; 009, Polarizing beam splitter; 010, Quarter wave plate; 011, Fast reflector; 012, Second dichroic mirror; 013, First narrowband filter; 014, First condenser lens; 015, CMOS beacon detector; 016, Second narrowband filter; 017, Second condenser lens; 018, APD detector. Detailed Implementation

[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] To address the above problems, this invention proposes a laser communication terminal based on an ultra-compact laser combiner, see attached figure. Figure 1 The communication terminal includes a laser multiplexer module, an optical antenna module, a beacon receiver module, a signal receiver module, and a beam splitter module.

[0023] The beam combiner module includes a beacon laser emitter 001, a signal laser emitter 002, a beam shaper 003, a beam shaper 004, a reflector 005, and a first dichroic mirror 006. The beacon laser emitter 001 emits a laser signal with a wavelength of 808 nm, which is shaped by the beam shaper 003 and reflected by the reflector 005 onto the first dichroic mirror 006. The signal laser emitter 002 emits a laser signal with a wavelength of 1540 nm, which is shaped by the beam shaper 004 and also incident on the first dichroic mirror 006. On the first dichroic mirror 006, the 808 nm wavelength is reflected, and the 1540 nm wavelength is transmitted, combining the two beams into one that enters the main optical path. A beacon is a reference optical signal with a specific wavelength, known direction, and positioning or guidance function, used for spatial positioning, attitude measurement, or target alignment. In this invention, a beacon specifically refers to an 808nm wavelength laser beam emitted by the communication peer or received by the local end. This beam does not carry communication data but serves as a reference light source for obtaining location information. In this embodiment, the beacon light is used to determine the spatial direction or angle of the peer laser communication device (e.g., a satellite, drone, or ground station) relative to the local laser communication terminal. When the externally incident beacon light is filtered and focused to form a spot on the CMOS image sensor, the system can obtain its position in the image coordinate system by imaging and centroid extraction of this spot. This position corresponds to the incident angle of the beacon light source and can indirectly reflect the angle or offset information of the beacon light source in space.

[0024] The optical antenna module includes a primary mirror 007, a secondary mirror 008, and a fast-reflecting mirror 011. The antenna has a magnification of 10x and can both reduce the received external light beam and expand and collimate the internally emitted light beam. Here, the beam emitted by the laser combiner is reflected by the polarizing beam splitter 009, passes through a quarter-wave plate 010, and is reflected by the fast-reflecting mirror 011 into the optical antenna module. Within the optical antenna module, it is further collimated and expanded before exiting into free space. Specifically, the main laser beam emitted by the laser combiner module is first reflected by the polarizing beam splitter 009, then its polarization state is adjusted by the quarter-wave plate 010, and finally reflected by the fast-reflecting mirror 011 and guided into the optical antenna module. After entering the optical antenna module, the main laser beam is reflected sequentially by the secondary mirror 008 (convex parabolic structure) and the primary mirror 007 (concave parabolic structure), forming an off-axis two-reflector beam-expanding optical path structure. In this structure, by rationally designing the curvature radius, relative position, and installation angle of the primary mirror 007 and the secondary mirror 008, the diameter of the laser beam spot gradually expands during reflection, thus achieving beam expansion. Simultaneously, through geometric control of the optical path, the output beam achieves good parallelism, i.e., collimated output. The magnification of the optical antenna is approximately 10 times, indicating that the effective aperture of the output beam is significantly larger than the initial laser beam, which is beneficial for improving the energy concentration and directional stability of the laser during long-distance transmission.

[0025] The beacon receiving module includes an 808nm first narrowband filter 013, a first focusing mirror 014, and a CMOS (Complementary Metal-Oxide-Semiconductor) beacon detector 015. The beacon light is received by the optical antenna module, first reflected by the primary mirror 007 to the secondary mirror 008, then reflected by the secondary mirror 008 to the fast reflector 011, reflected again by the fast reflector 011, transmitted through a quarter-wave plate 010, and then transmitted through a polarizing beam splitter 009. It is then transmitted to the second dichroic mirror 012, where the 808nm wavelength is reflected into the beacon receiving module. First, stray light is filtered out by the 808nm first narrowband filter 013, and then the first focusing mirror 014 converges the light spot onto the CMOS beacon detector 015. The CMOS beacon detector 015 performs imaging analysis on the light spot and calculates the centroid of the light spot to obtain its position information. Specifically, the first narrowband filter (013) is used for wavelength selective transmission of incident light. Its center wavelength is set to the target wavelength of the beacon laser, 808 nm, and its bandwidth is controlled within ±2 nm. That is, only light signals with wavelengths between approximately 806 nm and 810 nm are allowed to pass through, while light of other wavelengths will be effectively suppressed. During the operation of the laser communication terminal, the receiving path may be exposed to multiple ambient light sources simultaneously, such as sunlight, starlight, ground reflected light, or stray light generated by other devices. These light sources usually have continuous or multi-peak broadband characteristics, which may interfere with the detection and identification of beacon light. By setting the first narrowband filter in the beacon receiving optical path, the background light in the non-target wavelength range can be effectively filtered out, allowing only the beacon laser located in the 808±2 nm range to pass through, thereby improving the signal-to-noise ratio of the spot signal in the imaging system and enhancing the accuracy of subsequent centroid extraction and position information calculation.

[0026] The signal receiving module includes a 1563nm second narrowband filter 016, a second focusing mirror 017, and an APD (Avalanche Photodiode) detector 018. The signal light is received by the optical antenna module, first reflected by the primary mirror 007 to the secondary mirror 008, then reflected by the secondary mirror 007 to the fast reflector 011. After reflection on the fast reflector 011, it is transmitted through a quarter-wave plate 010, then through a polarizing beam splitter 009, and finally transmitted to the second dichroic mirror 012. The 1563nm wavelength is transmitted through the second dichroic mirror 012 into the signal receiving module. First, stray light is filtered out by the 1563nm second narrowband filter 016, then the second focusing mirror 017 converges the light spot onto the APD detector 018, where the APD detector 018 receives the signal light.

[0027] The beam splitter module includes a quarter-wave plate 010, a polarizing beam splitter 009, and a second dichroic mirror 012. The function of the beam splitter module is to separate the polarization state and wavelength of the main laser beam from the externally incident laser beam, thereby achieving effective path isolation between the emitted and received light in the optical path. Specifically, after the main laser beam is output from the laser combiner module, it is first reflected by the polarizing beam splitter 009, then transmitted through the quarter-wave plate 010, and after being reflected by the fast reflector 011, it enters the optical antenna module, realizing the laser beam output. The externally incident laser beam, after being received by the optical antenna module, returns along the same path, and after being transmitted again through the quarter-wave plate 010, its polarization direction is now orthogonal to its incident direction, thus enabling it to pass through the polarizing beam splitter 009, completing the path separation from the emitted light. Further, the incident light reaches the second dichroic mirror 012, where wavelength separation is performed according to different wavelengths. The 808nm wavelength is reflected to the beacon receiving module, while the 1563nm wavelength is transmitted to the signal receiving module. Through the aforementioned joint separation mechanism of polarization state and wavelength, the beam splitter module can achieve efficient decoupling of the transmission and reception paths within the common optical path system of laser communication, ensuring a compact system structure and non-interference of functions, thus meeting the requirements of miniaturization and high precision of laser communication terminals.

[0028] In the aforementioned optical path, the emission axes of the beacon emitting laser 001 and the signal emitting laser 002 are parallel. A beam shaping mirror 003 is located between the beacon emitting laser 001 and the reflector 005, with the reflector 005 situated on the beacon emission optical path. A beam shaping mirror 004 is located between the beacon emitting laser 002 and the first dichroic mirror 006, with the first dichroic mirror 006 located behind the beam shaping mirror 004. The primary mirror 007 in the optical antenna module is parallel to the optical axis of the secondary mirror 008, but must be installed off-axis. The fast reflector 011 is located after the secondary mirror 008 and is installed at a 45° angle. The quarter-wave plate 010 is located between the fast reflector 011 and the polarizing beam splitter 009, and can be installed horizontally. The polarizing beam splitter 009 is installed at a 45° angle and is coaxial with the quarter-wave plate 010 and the second dichroic mirror 012. The second dichroic mirror 012 is simultaneously located in both the beacon receiving optical path and the signal receiving optical path. A first narrowband filter 013 is located between a second dichroic mirror 012 and a first condenser lens 014, and a CMOS beacon detector 015 is mounted at the focal plane of the first condenser lens 014. A second narrowband filter 016 is located between a second dichroic mirror 012 and a second condenser lens 017, and an APD detector 018 is mounted at the focal plane of the second condenser lens 017.

[0029] In the above technical solution, the laser beam combiner module is a highly integrated module, employing miniature beam combining elements. The optical antenna is an off-axis dual-mirror structure, avoiding the optical obstruction problem of coaxial dual-mirror setups and reducing energy loss. The primary mirror 007 of the optical antenna module is a concave parabolic mirror, and the secondary mirror 008 is a convex parabolic mirror. Their optical axes are parallel but not coaxial, and the optical magnification is 10x. The primary mirror 007 and secondary mirror 008 are installed according to a preset off-axis geometry, ensuring that the incident or emitted beam forms a clear spot after multiple reflections between the two mirrors, and guaranteeing the beam quality after beam expansion or contraction. The fast-reflecting mirror 011 can precisely control the laser beam direction and quickly respond to and track the target's movement. The quarter-wave plate 010 is a polarization phase adjustment element, which can convert linearly polarized light into circularly polarized light, reducing the influence of the laser output environment. It can also convert circularly polarized light into linearly polarized light with a polarization direction perpendicular to the original polarization direction after passing through the quarter-wave plate again. Used in conjunction with the polarizing beam splitter 009, it splits the emitted and received light beams. The polarizing beam splitter 009 reflects S-polarized light and transmits P-polarized light. The second dichroic mirror 012 reflects an 808nm wavelength and transmits a 1563nm wavelength. The center wavelengths of the first narrowband filter 013 and the second narrowband filter 016 are 808nm and 1563nm, respectively, with a bandwidth of ±2nm. The first condenser lens 014 adopts a multi-lens structure, which can effectively reduce aberrations and chromatic aberration. The first condenser lens 014 adopts a multi-lens structure, which is composed of two or more lens elements with different optical parameters combined in a preset order and spacing. Compared to a single lens, this structure, by rationally combining lenses with different radii of curvature, refractive indices, and thicknesses, can effectively compensate for image quality distortions caused by spherical aberration, coma, and chromatic aberration while converging the laser beam, thus improving the clarity and stability of the converged light spot. In this embodiment, the first focusing lens 014 is used to precisely focus the 808nm wavelength beacon light reflected from the second dichroic mirror 012 onto the CMOS beacon detector 015, therefore requiring high imaging quality. The multi-lens structure not only ensures the imaging quality of the light spot, which is beneficial for the accuracy of subsequent image recognition and centroid positioning calculations, but also has the advantages of compact structure and modular packaging, facilitating the miniaturization and engineering implementation of the entire beacon receiving module. The CMOS beacon detector 015 can effectively respond to an 808nm wavelength and has a pixel size of 5.5µm. The APD detector 018 can convert optical signals into electrical signals and has high gain.

[0030] Compared with existing technologies, this invention proposes a laser communication terminal based on an ultra-compact laser combiner, achieving miniaturization, lightweighting, and low cost of the laser communication terminal, and has the following beneficial effects: On the one hand, it significantly reduces the size and weight. By innovatively integrating the beacon laser and the signal laser into a single laser multiplexer module, it eliminates the large amount of redundant space and connecting components required when the two are separate in traditional solutions. This results in a significant reduction in the overall size and greatly improves the system's adaptability and feasibility in space-constrained environments.

[0031] On the other hand, it significantly simplifies the optical path structure. In traditional laser communication systems, the beacon laser and signal laser operate as separate, complex optical path systems that are susceptible to interference. This invention integrates the two, achieving a high degree of integration and optimization of the optical path. This reduces a large number of optical components and optical path connection nodes, lowering the risk of signal loss and interference during transmission. The simplified optical path not only improves the transmission efficiency of optical signals but also reduces the probability of failures caused by optical path complexity, enhancing the stability and reliability of the system.

[0032] Thirdly, it reduces costs and increases integration. Integrated design reduces the number of discrete components, thereby lowering costs in procurement, assembly, and debugging. At the same time, highly integrated laser multiplexer modules help to miniaturize and integrate the entire laser communication system, facilitating the integration of more functional modules within a limited space and improving the overall performance and functionality of the system.

[0033] The above are merely embodiments of this application and are not intended to limit the scope of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of the claims of this application.

Claims

1. A laser communication terminal based on an ultra-compact laser multiplexer, characterized in that, include: A laser combining module is used to combine laser beams of different wavelengths into a single main laser beam through a spatial path. An optical antenna module is used to expand, collimate, and emit the main laser beam to be emitted, as well as to receive externally incident laser beams. The beam splitter module is used to separate the polarization state and wavelength of the main laser beam from the externally incident laser beam, guide the main laser beam to the optical antenna module, and guide the externally incident laser beam to the beacon receiving module and the signal receiving module respectively. The beacon receiving module is used to receive and process the beacon light signal used for position information acquisition in the externally incident laser beam, and output the corresponding position information; The signal receiving module is used to receive and process the optical signal carrying communication information in the externally incident laser beam, and output the corresponding electrical signal.

2. The laser communication terminal according to claim 1, characterized in that, The laser combining module includes: a beacon emitting laser (001) for emitting a beacon laser beam of a first wavelength; a signal emitting laser (002) for emitting a signal laser beam of a second wavelength; a first beam shaping mirror (003) for collimating and shaping the beacon laser beam of the first wavelength; a second beam shaping mirror (004) for collimating and shaping the signal laser beam of the second wavelength; a reflector (005) for reflecting the shaped beacon laser beam of the first wavelength to a first dichroic mirror (006) to combine it with the signal laser beam of the second wavelength; and the first dichroic mirror (006) for combining the shaped beacon laser beam of the first wavelength and the shaped signal laser beam of the second wavelength into a main laser beam.

3. The laser communication terminal according to claim 2, characterized in that, The optical antenna module includes a primary mirror (007), a secondary mirror (008), and a fast reflector (011). When receiving an externally incident beacon laser beam or signal laser beam, the primary mirror (007) reflects the beacon laser beam or signal laser beam to the secondary mirror (008), and the secondary mirror (008) further reflects the beacon laser beam or signal laser beam to the fast reflector (011). When emitting a main laser beam, the fast reflector (011) guides the main laser beam to the secondary mirror (008), the secondary mirror (008) reflects the main laser beam back to the primary mirror (007), and the primary mirror (007) expands and collimates the laser beam before it is emitted into free space.

4. The laser communication terminal according to claim 3, characterized in that, The beam splitting module includes a quarter-wave plate (010), a polarizing beam splitter (009), and a second dichroic mirror (012). The polarizing beam splitter (009) is used to reflect the main laser beam to the quarter-wave plate (010), and the quarter-wave plate (010) is used to transmit the main laser beam and allow it to enter the optical antenna module via the fast reflector (011); The quarter-wave plate (010) and the polarizing beam splitter (009) are used to transmit the beacon laser beam to be received in sequence, and the second dichroic mirror (012) is used to reflect the beacon laser beam to be received to the beacon receiving module. The quarter-wave plate (010), the polarizing beam splitter (009), and the second dichroic mirror (012) are used to sequentially transmit the signal light to be received, so that the signal laser beam to be received enters the signal receiving module.

5. The laser communication terminal according to claim 4, characterized in that, The beacon receiving module includes a first narrowband filter (013), a first focusing lens (014), and a CMOS beacon detector (015). The first narrowband filter (013) is used to filter out stray light of non-target wavelengths. The first focusing lens (014) is used to focus the received beacon laser beam of the first wavelength onto the CMOS beacon detector (015). The CMOS beacon detector (015) is used to image the light spot formed on the detector surface by the focused beacon laser beam and output the position information of the light spot.

6. The laser communication terminal according to claim 5, characterized in that, The signal receiving module includes a second narrowband filter (016), a second focusing lens (017), and an APD detector (018). The second filter (016) is used to filter out background stray light, the second focusing lens (017) is used to focus the signal laser beam onto the APD detector (018), and the APD detector (018) is used to receive the signal laser beam and convert the signal laser beam into an electrical signal.

7. The laser communication terminal according to claim 2, characterized in that, The beacon emitting laser (001) emits at a wavelength of 808 nm, and the signal emitting laser (002) emits at a wavelength of 1540 nm. The reflector (005) is disposed between the beacon emitting laser (001) and the first dichroic mirror (006) to guide the 808 nm laser to the first dichroic mirror (006). The first beam shaping mirror (003) is disposed between the beacon emitting laser (001) and the reflector (005); the second beam shaping mirror (004) is disposed between the signal emitting laser (002) and the first dichroic mirror (006).

8. The laser communication terminal according to claim 4, characterized in that, The first dichroic mirror (006) reflects 808nm wavelength light and transmits 1540nm wavelength light; the primary mirror (007) is a concave parabolic reflector, the secondary mirror (008) is a convex parabolic reflector, and the optical antenna module has a magnification of 5-10 times; the fast reflector (011) is obliquely installed behind the secondary mirror (008) to change the beam direction and adjust the emission direction to achieve target tracking.

9. The laser communication terminal according to claim 4, characterized in that, The quarter-wave plate (010) is disposed between the fast reflector (011) and the polarizing beam splitter (009) to realize the conversion between linearly polarized light and circularly polarized light; The polarizing beam splitter (009) is installed at an angle, which can reflect S-polarized light and transmit P-polarized light; The second dichroic mirror (012) is used to reflect the 808nm beacon laser beam to the beacon receiving module and transmit the 1540nm communication laser beam to the signal receiving module; The first narrowband filter (013) has a center wavelength of 808nm and a bandwidth of ±2nm; The second narrowband filter (016) has a center wavelength of 1563nm and a bandwidth of ±2nm.

10. The laser communication terminal according to claim 6, characterized in that, The first focusing lens (014) and the second focusing lens (017) adopt a multi-piece structure; The primary mirror (007) and the secondary mirror (008) are arranged parallel to each other but off-axis; The fast reflector (011), the quarter-wave plate (010), the polarizing beam splitter (009), and the second dichroic mirror (012) are arranged coaxially.

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