A small airborne optical communication system based on piezoelectric scanning table

Abstract

The application discloses a small-sized airborne optical communication system based on a piezoelectric scanning platform, which comprises a coarse tracking module, a fine tracking module and a signal transceiving module; a multimode laser of a communication transmitting end transmits coarse beacon light, which is emitted after collimation of a transmitting lens, and is irradiated into the coarse tracking module of a receiving telescope on the opposite side after propagating in free space for a distance; coarse tracking receiving lenses in the receiving telescope focus the coarse beacon light into a coarse tracking camera target surface; then, the pointing angle of the holder is adjusted according to the position error signal of the focused light spot, and the initial acquisition and alignment of the communication parties are completed. The application is small-sized and light-weighted, the weight of the whole system is controlled to be about 1 kg, the tracking and aiming precision is high, the camera in the fine beacon loop can distinguish up to 4.7 mu rad of light field angle change, the link loss is low, the position of the single-mode optical fiber can be accurately adjusted, the coupling efficiency is the highest, meanwhile, all the lenses in the system are coated with antireflection films responding to the wavelength, and the transmittance of the system itself is improved.

Description

Technical Field

[0001] This invention relates to the fields of free-space laser communication and quantum communication, and in particular to a small airborne optical communication system based on a piezoelectric scanning stage that can be used for both classical optical communication and quantum communication. Background Technology

[0002] Free-space optical (FSO) communication is a communication technology based on the propagation of optical signals in free space. It boasts advantages such as high bandwidth, high speed, and resistance to electromagnetic interference, and is widely used in satellite communication, drone communication, and high-speed terrestrial communication. Among these, FSO based on drone platforms has attracted considerable attention due to its high mobility and flexible deployment. In recent years, quantum communication, with its enhanced security, has garnered significant attention and research. Currently, quantum communication between satellites and ground stations and between terrestrial optical fibers are existing. Drone-based quantum communication offers advantages such as high flexibility, low cost, and rapid deployment, providing a new solution for quantum information transmission. However, free-space quantum communication places higher demands on the system's tracking accuracy and the loss of the signal optical link to facilitate high-speed and low-error-rate transmission of quantum keys.

[0003] Existing free-space laser communication and quantum communication technologies mostly employ large-aperture reflecting telescopes as optical antennas, utilizing an acquisition, point, and tracking (APT) system to align and track the beacon optical link, followed by signal optical communication between the two telescopes. However, existing optical communication systems are generally large and heavy, making them unsuitable for direct application on low-payload UAV platforms. Classical free-space optical communication systems do not have high precision requirements for the tracking system, and are therefore unsuitable for the high alignment accuracy, low loss, and low bit error rate requirements of quantum communication. Therefore, it is necessary to research a high-precision, small-scale, and lightweight airborne optical communication system that can be applied to both classical and quantum communication. Summary of the Invention

[0004] Purpose of the invention: The purpose of this invention is to provide a small airborne optical communication system based on a piezoelectric scanning stage that can be applied to both classical optical communication and quantum communication.

[0005] Technical Solution: The small airborne optical communication system based on a piezoelectric scanning stage described in this invention includes a coarse tracking module, a fine tracking module, and a signal transceiver module. A multimode laser at the communication transmitter emits a coarse beacon light, which is collimated by a transmitting lens and then emitted. After propagating a distance in free space, it illuminates the coarse tracking module of the receiving telescope on the opposite side. The coarse tracking receiving lens in the receiving telescope focuses the coarse beacon light onto the target surface of the coarse tracking camera. Then, based on the position error signal of the focused spot, the pointing angle of the pan-tilt unit is adjusted to complete the initial acquisition and alignment between the two communicating parties. Then the system enters... In the precision tracking stage, the signal light and the precision beacon light are emitted simultaneously. The signal light exits from the single-mode fiber, passes through the transceiver lens group, dichroic mirror, and optical antenna, and then exits. The precision beacon light exits from the single-mode fiber, is collimated by an aspherical lens, and exits from the center of the window. After propagating a distance in free space, it is received by the signal transceiver module of the communication receiver. Subsequently, it is focused onto the camera target by the receiving lens group of the precision beacon light. By calculating the position error signal of the focused spot of the precision beacon light in real time, the piezoelectric scanning stage is driven to adjust its position in real time to maintain the high coupling efficiency of the single-mode fiber.

[0006] Furthermore, the coarse beacon module includes a camera, a coarse beacon receiving lens group, a filter, a coarse beacon transmitting lens, a multimode fiber, and an 878.6 nm laser. The 878.6 nm laser emits coarse beacon light, which is sequentially focused onto the camera target surface by the coarse beacon transmitting lens, the filter, and the coarse beacon receiving lens group.

[0007] Furthermore, the precision tracking module includes a refractive optical antenna, a dichroic beam splitter, a precision beacon beam focusing lens group, a precision beacon beam emitting lens group, a precision tracking camera, and an 830 laser; the signal light and the precision beacon beam are emitted simultaneously. The signal light exits from the single-mode fiber, passes through the refractive optical antenna, and then exits, while the precision beacon beam exits from the single-mode fiber, passes through the precision beacon beam focusing lens group and the precision beacon beam emitting lens group, and then exits. After propagating a distance in free space, it is received by the signal transceiver module of the communication receiver, and then focused onto the target surface of the precision tracking camera by the precision beacon receiving lens group.

[0008] Furthermore, the refractive optical antenna includes a window, a biconvex lens, a meniscus lens, and a biconcave lens.

[0009] Furthermore, the precision beacon focusing lens group includes a third meniscus lens, a first biconcave lens, a biconvex lens, and a second biconcave lens.

[0010] Furthermore, the precision beacon light emitting mirror assembly includes a right-angle prism, a precision beacon emitting lens, and a multimode optical fiber.

[0011] Furthermore, the signal transceiver module includes a signal optical transceiver mirror group, a piezoelectric scanning displacement stage, a single-mode optical fiber, and a circulator. It drives the piezoelectric scanning displacement stage to adjust its position by calculating the position error signal of the focused spot of the fine beacon light.

[0012] Furthermore, the signal transceiver lens group sequentially includes a first meniscus lens, a second meniscus lens, and a plano-convex lens.

[0013] Beneficial Effects: Compared with the prior art, this invention has the following significant advantages: It adopts a compact, transmissive optical telescope structure design. A piezoelectric scanning displacement stage is used in the precision tracking loop to replace the piezoelectric fast-reflecting mirror in the traditional tracking system, achieving precision tracking feedback adjustment. The positional accuracy of the piezoelectric scanning displacement stage is 7 nm, enabling high-precision position adjustment of the single-mode fiber, maximizing its coupling efficiency. It is small and lightweight, with the entire system weighing approximately 1 kg. It boasts high tracking accuracy, with the camera in the precision beacon loop able to resolve light field angle changes as high as 4.7 µrad. It exhibits low link loss, as the high-precision piezoelectric scanning stage can precisely adjust the position of the single-mode fiber, maximizing coupling efficiency. Furthermore, all lenses in the system are coated with anti-reflection films that respond to the wavelength, improving the system's transmittance. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the overall structure of a small airborne optical communication system based on a piezoelectric scanning station;

[0015] Figure 2 Optical path structure diagram of the tracking module and beacon transceiver module;

[0016] Figure 3 This is a schematic diagram of the piezoelectric scanning stage. Detailed Implementation

[0017] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0018] The small airborne optical communication system based on a piezoelectric scanning stage described in this invention is suitable for use on unmanned aerial vehicles (UAVs) for free-space optical communication and quantum communication. Its specific structure consists of three parts: a coarse-tracking module, a fine-tracking module, and a signal transceiver module. A schematic diagram of the entire system structure is shown below. Figure 1 As shown.

[0019] The coarse beacon module includes a camera, a coarse beacon receiving lens group, a filter, a coarse beacon transmitting lens, MMF (multimode fiber), and an 878.6 nm laser.

[0020] like Figure 2As shown, the precision tracking module comprises a refractive optical antenna, a dichroic beam splitter 5, a precision beacon beam focusing lens group, a precision beacon beam emitting lens group, a precision tracking camera, an 830 laser, and other components. The refractive optical antenna includes a window 1, a biconvex lens 2, a meniscus lens 3, and a biconcave lens 4; the precision beacon beam focusing lens group includes a third meniscus lens 12, a first biconcave lens 13, a biconvex lens 14, and a second biconcave lens 15; the precision beacon beam emitting lens group includes a right-angle prism 16, a precision beacon emitting lens 17, and a multimode fiber MMF 18.

[0021] The signal transceiver module consists of a signal optical transceiver mirror assembly, a piezoelectric scanning displacement stage, an SMF (single-mode fiber) optical fiber, and a circulator. The signal optical transceiver mirror assembly includes a first meniscus lens, a second meniscus lens, and a plano-convex lens. The system design parameters of this invention are shown in Table 1.

[0022] Table 1

[0023] category parameter Light aperture 50 mm Operating wavelength Signal light @1550 nm; fine beacon light @830 nm; coarse beacon light @878.6 nm Receiving half field of view Signal light@200 μrad; fine beacon light@2 mrad; coarse beacon light@35 mrad focal length Signal beam @ 98.1 mm; fine beacon beam @ 530 mm; coarse beacon beam @ 100 mm single-mode fiber UHNA1, core 2.5 μm, MFD=4.8 μm; NA=0.28 Output beam divergence angle Signal light@98 μrad; fine beacon light@5 mrad; coarse beacon light@35 mrad Thick beacon camera The target surface size is 4.97 mm * 3.72 mm, the resolution is 720 * 540, and the pixel size is 6.9 μm. Precision beacon camera The target surface size is 6.5 mm * 5.4 mm, the resolution is 2600 * 2160, and the pixel size is 2.5 µm. Single pixel resolution 4.7 µrad piezoelectric scanning displacement stage Maximum stroke range ±30 µm, displacement accuracy 7 nm, resonant frequency 1.5 kHz

[0024] The specific implementation plan is as follows:

[0025] (1) Initial capture and alignment

[0026] The 878.6 nm multimode laser at the communication transmitter emits a coarse beacon beam. After being collimated by the transmitting lens, the beam exits with a divergence angle of 1°. After propagating a certain distance in free space, it illuminates the coarse-tracking module of the receiving telescope on the other side. The coarse-tracking receiving lens in the receiving telescope focuses the coarse beacon beam onto the coarse-tracking camera target surface. Then, based on the position error signal of the focused spot, the pointing angle of the gimbal is adjusted to complete the initial acquisition and alignment between the two communicating parties.

[0027] (2) Precise tracking and signal transmission

[0028] After initial acquisition and tracking, the system enters the fine tracking phase. During this phase, a 1550 nm signal light and an 830 nm fine beacon light are emitted simultaneously. The signal light exits from the single-mode fiber, passing through the transceiver lens group, dichroic mirror, and optical antenna before exiting at a half-divergence angle of 50 µrad. The fine beacon light, also from the single-mode fiber, is collimated by an aspherical lens and exits from the center of the window at a half-emission angle of 5 mrad. After propagating a certain distance in free space, it is received by the optical antenna at the communication receiver and then focused onto the camera target surface by the receiving lens group of the fine beacon. The position error signal of the focused spot of the fine beacon light is calculated in real time to drive the piezoelectric scanning displacement stage for real-time position adjustment, maintaining the high coupling efficiency of the 1550 nm single-mode fiber. A schematic diagram of the piezoelectric scanning displacement stage is shown below. Figure 3 As shown.

[0029] This invention discloses a small airborne optical communication system with a two-stage beacon tracking and aiming feedback loop, including a coarse beacon tracking feedback loop and a fine beacon feedback loop. The system's optical antenna has a diameter of 50 mm and employs a compact optical design, keeping the overall system weight below 1.5 kg. A significant feature of this invention is the use of a piezoelectric scanning stage at the signal receiving end to adjust the position of the single-mode fiber in real time, compensating for the decrease in coupling efficiency caused by alignment errors. The fine beacon feedback loop, formed by the piezoelectric scanning displacement stage and the fine beacon camera, significantly improves the system's tracking accuracy and fiber coupling efficiency. Compared to traditional feedback loops based on fast-reflecting mirrors, the piezoelectric scanning stage has a smaller size and weight, thus enabling a more compact and lightweight system while achieving high tracking accuracy. This invention's piezoelectric displacement stage-based laser communication system offers advantages such as small size and lightweight design, high tracking accuracy, and applicability to both classical and quantum optical communication, making it particularly suitable for use on unmanned aerial vehicles (UAVs) for free-space optical and quantum communication.

Claims

1. A small airborne optical communication system based on a piezoelectric scanning stage, characterized in that, The system includes a coarse tracking module, a fine tracking module, and a signal transceiver module. At the communication transmitter, a multimode laser emits a coarse beacon beam, which is collimated by a transmitting lens and then emitted. After propagating a distance in free space, it illuminates the coarse tracking module of the receiving telescope on the opposite side. The coarse tracking receiving lens in the receiving telescope focuses the coarse beacon beam onto the coarse tracking camera target surface. Then, based on the position error signal of the focused spot, the pointing angle of the pan-tilt unit is adjusted to complete the initial acquisition and alignment between the two communicating parties. Next, the system enters the fine tracking phase, where the signal beam and fine beacon beam are emitted simultaneously. The signal beam exits from a single-mode fiber, passes through a transceiver lens group, a dichroic mirror, and an optical antenna, and then exits. The fine beacon beam exits from a single-mode fiber, is collimated by an aspherical lens, and exits from the center of the window. After propagating a distance in free space, it is received by the signal transceiver module at the communication receiver end and then focused onto the camera target surface by the fine beacon beam receiving lens group. By calculating the position error signal of the focused spot of the fine beacon beam in real time, the piezoelectric scanning stage is driven to perform real-time position adjustments to maintain the high coupling efficiency of the single-mode fiber.

2. The small airborne optical communication system based on a piezoelectric scanning stage according to claim 1, characterized in that, The coarse beacon module includes a camera, a coarse beacon receiving lens group, a filter, a coarse beacon transmitting lens, a multimode fiber, and an 878.6 nm laser. The 878.6 nm laser emits coarse beacon light, which is focused onto the camera target surface in sequence through the coarse beacon transmitting lens, the filter, and the coarse beacon receiving lens group.

3. The small airborne optical communication system based on a piezoelectric scanning stage according to claim 1, characterized in that, The precision tracking module includes a refractive optical antenna, a dichroic beam splitter (5), a precision beacon beam focusing lens group, a precision beacon beam emitting lens group, a precision tracking camera, and an 830 laser. The signal light and the precision beacon light are emitted simultaneously. The signal light is emitted from a single-mode fiber and then emitted after passing through the refractive optical antenna, while the precision beacon light is emitted from a single-mode fiber and then emitted after passing through the precision beacon beam focusing lens group and the precision beacon beam emitting lens group. After propagating a distance in free space, it is received by the signal transceiver module of the communication receiver and then focused onto the target surface of the precision tracking camera by the precision beacon receiving lens group.

4. The small airborne optical communication system based on a piezoelectric scanning stage according to claim 3, characterized in that, The refractive optical antenna includes a window (1), a biconvex lens (2), a meniscus lens (3), and a biconcave lens (4).

5. The small airborne optical communication system based on a piezoelectric scanning stage according to claim 3, characterized in that, The fine beacon focusing lens group includes a third meniscus lens (12), a first biconcave lens (13), a biconvex lens (14), and a second biconcave lens (15).

6. The small airborne optical communication system based on a piezoelectric scanning stage according to claim 3, characterized in that, The precision beacon light emitting mirror assembly includes a right-angle prism (16), a precision beacon emitting lens (17), and a multimode fiber (18).

7. The small airborne optical communication system based on a piezoelectric scanning stage according to claim 3, characterized in that, The signal transceiver module includes a signal optical transceiver mirror group, a piezoelectric scanning displacement stage (9), a single-mode fiber (10), and a circulator (11). It drives the piezoelectric scanning displacement stage (9) to adjust its position by calculating the position error signal of the focused spot of the fine beacon light.

8. The small airborne optical communication system based on a piezoelectric scanning stage according to claim 7, characterized in that, The signal transceiver lens group includes a first meniscus lens (6), a second meniscus lens (7), and a plano-convex lens (8) in sequence.

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