An unmanned aerial vehicle communication system and method based on hollow core optical fiber

Abstract

This invention discloses a drone communication system and method based on hollow-core optical fiber, belonging to the field of drone communication technology. The system includes: a drone with a first single-fiber bidirectional optical module; a ground control station with a second single-fiber bidirectional optical module; and a cable reel mounted on the drone for winding and releasing hollow-core optical fiber. The two ends of the hollow-core optical fiber are optically connected to the first and second single-fiber bidirectional optical modules, respectively. When the drone flies and releases the hollow-core optical fiber from the cable reel, the first and second single-fiber bidirectional optical modules transmit uplink control commands and downlink video signals bidirectionally through the hollow-core optical fiber. This invention achieves lightweight fiber substrate to release axial weight quotas, significantly extending the cable laying distance and allowable operating radius while maintaining the same weight, and greatly reducing the cumulative transmission delay of optical signals.

Description

Technical Field

[0001] This invention relates to the field of unmanned aerial vehicle (UAV) communication technology, and in particular to a UAV communication system and method based on hollow optical fiber. Background Technology

[0002] In the field of unmanned aerial vehicle (UAV) communication and control, UAV systems using optical fiber as the physical transmission medium possess excellent anti-electromagnetic interference, counter-reconnaissance, and anti-interception capabilities. Unlike traditional UAVs that rely on radio frequency (RF) signal transmission, fiber optic UAVs connect to the ground control station via a long, thin optical fiber, enabling bidirectional data transmission. The optical signal is transmitted in the form of light pulses, which not only provides extremely strong anti-interference capabilities but also offers a wider bandwidth, allowing for real-time transmission of high-definition video footage, enabling operators to accurately identify targets.

[0003] Currently, fiber-optic guided unmanned aerial vehicle (UAV) systems mostly use traditional solid single-mode fiber (SMF) as the physical layer transmission medium. However, in practical engineering applications and combat environments, existing UAV communication architectures based on solid single-mode fiber have the following physical defects: First, the onboard load is excessive. Traditional solid single-mode optical fibers are entirely composed of high-density solid quartz glass for both the core and cladding, resulting in a large mass per unit length. As the fiber length increases, its weight increases linearly, and the volume and weight of the spool containing the fiber also increase accordingly. In ultra-long-distance operation scenarios, the weight of long-distance optical fibers can reach several kilograms, significantly reducing the effective payload of the UAV. The UAV must carry the entire roll of optical fiber throughout the flight, and the weight of the fiber drastically consumes power reserves and compresses the mission payload space, severely limiting flight speed and endurance.

[0004] Second, the operational radius is limited. Due to the limited volume and load capacity of the cable reel, the operational radius of current fiber optic UAVs is generally only 5 to 10 kilometers. Even for models with longer nominal ranges, the actual usable fiber length is often lower than the nominal value. This physical bottleneck directly limits the maximum permissible cable laying distance and operational depth of the UAV, preventing the system from providing sufficient safe operating distance.

[0005] Third, transmission delay is significant. The transmission speed of optical signals in traditional solid single-mode optical fibers is limited by the high refractive index of quartz glass (approximately 1.44–1.45), far below the speed of light in a vacuum. When the fiber optic link length extends to tens of kilometers, the kilometer-level cumulative transmission delay caused by the quartz medium becomes very significant. In scenarios such as high-speed target tracking and real-time control, this physical layer transmission lag results in perceptible delays in the images received by the pilot, making it impossible to implement high-dynamic real-time feedback control and severely impacting combat effectiveness.

[0006] In summary, existing UAV communication solutions based on solid single-mode optical fibers face insurmountable physical bottlenecks in terms of lightweight design, long-distance transmission, and high efficiency. In recent years, hollow-core antiresonant fiber has rapidly developed as a novel optical waveguide medium. Using air as its core material, it offers advantages such as ultra-low latency, weak nonlinearity, and resistance to electromagnetic interference. However, current research on hollow-core fiber primarily focuses on static ground applications. Existing technologies have not yet provided corresponding solutions for the systemic engineering challenges of lightweight fiber, long-distance release, and high-speed transmission simultaneously involved in dynamic UAV cable-laying communication. Summary of the Invention

[0007] To address the aforementioned technical problems, this invention provides a UAV communication system and method based on hollow optical fiber, aiming to achieve lightweighting of the optical fiber matrix to release axial weight quotas under the same length, to multiply the allowable operating radius under the same weight conditions, and to improve communication efficiency.

[0008] To achieve the above objectives, the technical solution of the present invention is as follows: A drone communication system based on hollow optical fiber, comprising: The drone is equipped with a first single-fiber bidirectional optical module. The ground control station is equipped with a second single-fiber bidirectional optical module. A wire storage spool, mounted on the UAV, is used to wind and release hollow optical fibers; One end of the hollow optical fiber extends through the storage spool into the UAV and is optically connected to the first single-fiber bidirectional optical module; the other end of the hollow optical fiber extends into the ground control station and is optically connected to the second single-fiber bidirectional optical module. The first single-fiber bidirectional optical module and the second single-fiber bidirectional optical module have complementary wavelengths and form a physical optical channel for simultaneous transmission of uplink control commands and downlink video signals through the same hollow optical fiber.

[0009] In the above scheme, the hollow optical fiber is a hollow anti-resonant optical fiber, which has an anti-resonant microstructure formed by multiple layers of thin-walled quartz capillaries surrounding a hollow air core.

[0010] In a further technical solution, the quartz filling factor f of the hollow optical fiber ranges from 34% to 36%, wherein the quartz filling factor f is defined as the ratio of the cross-sectional area of ​​the quartz material in the hollow optical fiber to the cross-sectional area of ​​the quartz matrix in a solid single-mode optical fiber with the same cladding outer diameter.

[0011] In the above scheme, the UAV is also equipped with a mode field adapter, and the hollow fiber is optically connected to the first single-fiber bidirectional optical module through the mode field adapter; the mode field adapter is used to adapt the mode field of the optical signal output by the first single-fiber bidirectional optical module to the hollow fiber.

[0012] In a further technical solution, the mode field adapter is a transition fiber, the end of which has a mode field transition structure, and the output end face of the mode field transition structure is directly fused and solidified with the light-incident end face of the hollow fiber.

[0013] In the above scheme, the mold field transition structure is one of the following: a reverse tapered structure, a thermo-expanded core structure, or a composite structure of tapered and thermo-expanded core.

[0014] In the above scheme, the transition fiber is a solid single-mode fiber.

[0015] In the above scheme, the ground control station is also equipped with an optical interconnect component, and the other end of the hollow fiber is optically connected to the optical interconnect component; the optical interconnect component is connected to the second single-fiber bidirectional optical module via a section of ground-end solid single-mode fiber.

[0016] In a further technical solution, the optical interconnect component is a beam-expanding fiber connector, which includes a pair of lenses for expanding and refocusing the optical signal emitted from the end face of the hollow fiber and then coupling it into the solid single-mode fiber at the ground end.

[0017] A UAV communication method based on hollow-core optical fiber, the method comprising: When the UAV is in flight and releases the hollow fiber from the storage spool configured on the UAV, the first single-fiber bidirectional optical module configured in the UAV and the second single-fiber bidirectional optical module configured in the ground control station simultaneously transmit uplink control commands and downlink video signals bidirectionally through the hollow fiber.

[0018] Through the above technical solution, the UAV communication system and method based on hollow optical fiber provided by the present invention have the following beneficial effects: (1) Significant weight reduction and improved flight performance. This invention introduces hollow anti-resonant fiber as the physical layer transmission medium, utilizing its high air content microstructure to achieve lightweight fiber substrate for the same length. The quartz fill factor of the hollow anti-resonant fiber is much lower than that of solid single-mode fiber, resulting in a higher fiber substrate weight reduction ratio. By reducing the substrate mass and releasing the axial weight quota, the payload capacity, flight speed, and endurance of the UAV are correspondingly improved, the motor power consumption during cable laying is reduced, and the attitude response sensitivity under high dynamic flight conditions is improved.

[0019] (2) The operating radius is significantly expanded under equal weight conditions, increasing the safety depth. Under the same weight constraint condition with a fixed quota of fiber core load allocated to the cable reel, since the mass per unit length of the hollow anti-resonant fiber is significantly lower than that of the solid single-mode fiber, the maximum allowable total cable length when using the hollow anti-resonant fiber in this invention is significantly increased compared to that of the solid single-mode fiber, and its cable expansion ratio increases as the quartz fill factor decreases. Without changing the overall takeoff axis weight, the allowable operating radius and operational safety depth of the UAV are expanded exponentially.

[0020] (3) Significantly improved communication efficiency and elimination of cumulative transmission lag. This invention is based on the hollow air core structure of hollow anti-resonant optical fiber, which reduces the limitation of the solid quartz matrix on the propagation speed of optical signals by the low refractive index medium of the physical layer, thus significantly improving the transmission speed of optical signals. Compared with solid single-mode optical fiber, the signal delay is significantly reduced, the communication efficiency is doubled, and the real-time control communication efficiency and high-definition image transmission response speed are significantly better than the traditional solid single-mode optical fiber communication architecture, effectively eliminating the kilometer-level cumulative transmission lag of optical signals and the demodulation delay of control commands. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below.

[0022] Figure 1 This is a schematic diagram of the architecture of a UAV communication system based on hollow optical fiber disclosed in this invention; Figure 2 This is a schematic diagram of the asymmetric optical path coupling link disclosed in this invention; Figure 3 A comparison of the cable lengths of solid single-mode fiber and hollow anti-resonant fiber under the same weight constraint conditions; Figure 4 A comparison of communication delay between hollow anti-resonant optical fiber and solid single-mode optical fiber at different transmission distances.

[0023] In the diagram: 1. UAV; 2. First single-fiber bidirectional optical module; 3. Mode field adapter; 4. Storage spool; 5. Hollow-core optical fiber; 6. Optical interconnect component; 7. Ground-end solid single-mode optical fiber; 8. Second single-fiber bidirectional optical module; 9. Ground control station. Detailed Implementation

[0024] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0025] This invention provides a UAV communication system and method based on hollow-core optical fiber, and specific embodiments are as follows: I. System Overall Architecture like Figure 1 As shown, the present invention provides a UAV communication system based on hollow optical fiber. The system architecture includes a UAV 1, a hollow optical fiber 5 as the physical transmission medium, and a ground control station 9. The hollow optical fiber 5 is preferably a hollow anti-resonant optical fiber, whose interior is composed of multiple layers of thin-walled quartz capillaries surrounding a hollow air core, forming an anti-resonant microstructure.

[0026] The UAV 1 is internally equipped with a first single-fiber bidirectional optical module (first BiDi optical module) 2 and a mode field adapter 3. The mode field adapter 3 is connected to the optical physical interface of the first single-fiber bidirectional optical module 2. A cable storage spool 4 is mounted on the bottom of the UAV 1 for winding and dynamically releasing hollow-core optical fiber 5. The ground control station 9 is internally equipped with an optical interconnect component 6 and a second single-fiber bidirectional optical module (second BiDi optical module) 8. The optical interconnect component 6 is connected to the second single-fiber bidirectional optical module 8 via a section of ground-end solid single-mode optical fiber 7.

[0027] The first single-fiber bidirectional optical module 2 and the second single-fiber bidirectional optical module 8 have complementary wavelengths and achieve full-duplex bidirectional optical signal transmission through the same hollow fiber 5. Specifically, the first single-fiber bidirectional optical module 2 converts the uplink electrical signal to be transmitted into an optical signal and couples it to the hollow fiber 5, while simultaneously converting the downlink optical signal received by the fiber into an electrical signal. The second single-fiber bidirectional optical module 8 has the same function as the first single-fiber bidirectional optical module 2, converting the downlink electrical signal into an optical signal for transmission to the sky end, while simultaneously converting the uplink optical signal received by the fiber into an electrical signal.

[0028] When the drone 1 flies and releases the hollow fiber 5 from the storage spool 4, the first single-fiber bidirectional optical module 2 and the second single-fiber bidirectional optical module 8 simultaneously transmit uplink control commands and downlink video signals bidirectionally through the hollow fiber 5.

[0029] II. Asymmetric Optical Path Coupling Layout like Figure 2 As shown, the mode field adapter 3 and the optical interconnect component 6 are respectively located at the sky end and the ground end. The present invention adopts an asymmetric optical path coupling layout to meet the dynamic anti-vibration requirements during flight and the active docking requirements at the ground end.

[0030] Specifically, in the sky end, the first single-fiber bidirectional optical module 2 is connected to the mode field adapter 3, and then connected to one end of the hollow fiber 5 via the mode field adapter 3; in the ground end, the other end of the hollow fiber 5 is connected to a section of solid single-mode fiber 7 at the ground end via the optical interconnect component 6, and then connected to the second single-fiber bidirectional optical module 8, thus forming a point-to-point physical optical communication link between the ground control station 9 and the UAV 1.

[0031] (a) Sky-end model field adapter The mode field adapter 3 at the air-end can be either a fully fiber-optic mode field adapter or a graded-index multimode fiber bridging mode field adapter. Considering the stringent requirements for connection point reliability due to the severe vibration and impact environment during UAV flight and cable laying, a fully fiber-optic mode field adapter is preferred.

[0032] The mode field adapter 3 is a transition fiber with a mode field transition structure at its end. The large mode field output end face of the mode field transition structure is directly and physically fused with the light input end face of the hollow fiber 5 at high temperature, so that the two fiber segments form an integral structure without relative displacement, which can effectively resist the vibration and impact during flight cable laying. In this embodiment, the transition fiber is a solid single-mode fiber.

[0033] Since the mode field diameter of hollow fiber 5 is much larger than that of solid single-mode fiber, direct splicing will lead to severe mode field mismatch and optical signal loss. Therefore, the end of the solid single-mode fiber needs to be structurally processed to form a mode field transition structure. This mode field transition structure can be achieved in the following ways: processing the fiber end into a reverse tapered structure, thermally expanding the fiber end, or combining tapering and thermal expansion. Among these methods, the reverse tapered structure has mature technology, controllable parameters, and uniform stress distribution in the formed tapered transition region, resulting in higher mechanical reliability. Therefore, this embodiment further prefers to use the reverse tapered structure.

[0034] The reverse tapered structure is a core diameter-gradient structure formed through micro-nano optical processing. Specifically, the end of the optical fiber is locally heated to a molten state and then tension is applied along the axial direction, causing the core diameter to smoothly shrink from the original diameter to the end diameter. This gradually evolves the mode field diameter of the transmitted optical signal from a small mode field to a large mode field to match the large mode field of the hollow fiber 5, achieving low-loss mode field matching between the two fibers. The large mode field output end face of the reverse tapered structure is directly fused and cured at high temperature with the light-incident end face of the hollow fiber 5.

[0035] (ii) Ground-side optical interconnect components In the ground-based section, the optical interconnect component 6 employs spatial optical coupling, preferably via a bundle-expanded fiber optic connector. Ground environments contain dust and other contaminants, and physical contact connections are prone to increased loss due to end-face wear or contamination. The bundle-expanded fiber optic connector includes paired lenses used to amplify and refocus the optical signal emitted from the end face of the hollow-core fiber 5 before coupling it into the solid single-mode fiber 7 at the ground end, achieving a low-loss, non-physical contact optical connection. This non-contact design prevents direct contact between the end faces, thus repeated insertions and removals do not cause end-face wear, and the parallel beam after amplification is insensitive to dust.

[0036] It is understandable that other non-physical contact spatial optical coupling schemes, such as fiber collimator pairs and free-space optical couplers, can also achieve the same function, and those skilled in the art can make equivalent substitutions according to actual engineering needs.

[0037] III. Fiber Optic Selection Guide The high-dynamic cable laying operations of unmanned aerial vehicles (UAVs) place stringent demands on the structural robustness and splicing reliability of optical fibers. Not all hollow-core fiber types can meet these engineering requirements. Taking hollow-core photonic bandgap fiber as an example, its cladding is composed of periodic, precise air-hole microstructures, and the light guiding mechanism is highly dependent on the strict periodicity of these microstructures. Under complex conditions such as axial bending, tensile stress, or vibration and shock, this structure is extremely prone to micro-damage, leading to the collapse of the photonic bandgap effect and a catastrophic increase in transmission loss. Furthermore, the splicing process between this type of fiber and solid single-mode fiber is extremely complex, and the air-hole structure is prone to collapse at high temperatures, resulting in high connection loss.

[0038] In contrast, the light guiding mechanism of hollow-core antiresonant fiber is based on the antiresonant reflection effect. Its cladding is composed of thin-walled quartz capillaries, resulting in a relatively simple structure and higher tolerance to local deformation. Even with a certain degree of geometric deformation, its antiresonant light guiding conditions can still be maintained, and performance degradation is gradual rather than collapse-like, which can meet the engineering requirements of high-dynamic cable laying scenarios for UAVs. Therefore, this embodiment preferably uses hollow-core antiresonant fiber as the physical layer transmission medium.

[0039] It should be further clarified that the core of this invention lies in achieving lightweight, ultra-long-distance, high-speed communication for UAVs using hollow-core light-guiding media, rather than being limited to a specific type of hollow-core optical fiber. Any alternative hollow-core optical fiber (such as photonic crystal fiber) based on the same or similar hollow-core light-guiding principle and capable of achieving the same or similar lightweight and high-speed communication functions is an equivalent implementation of the technical concept of this invention and falls within the protection scope of this invention.

[0040] IV. Lightweighting and Extended Cable Distance With the outer diameter of the cladding being 125 μm and the theoretical mass of pure quartz glass per kilometer A solid single-mode fiber is used as a comparison benchmark. This embodiment controls the internal geometry of the hollow antiresonant fiber to adjust its quartz fill factor. Within the range of 34% to 36%, the quartz fill factor f is defined as the ratio of the cross-sectional area of ​​the quartz material in a hollow-core optical fiber to the cross-sectional area of ​​the quartz matrix in a solid single-mode optical fiber with the same cladding outer diameter. The corresponding mass of pure quartz glass per kilometer... The corresponding weight reduction is 9.18 g / km to 9.72 g / km. This represents the matrix weight reduction ratio between hollow-core antiresonant fiber and solid single-mode fiber. The following calculation formula is satisfied: ; Calculations show that the fiber substrate weight reduction ratio The percentage is 64.00% to 66.00%. The total bearing length of the storage spool 4 is... When using optical fibers, the matrix mass is directly reduced compared to solid single-mode fibers. Satisfying the formula: ; In a specific application example, when the total length of the released optical fiber... When the length is fixed at 10.00 km, the total mass of the quartz corresponding to the solid single-mode fiber is 270.00 g, while the total mass of the hollow anti-resonant fiber in this embodiment is only 91.80 g to 97.20 g, directly reducing the axial weight by 172.80 g to 178.20 g. This lightweight reduction benefit of the substrate for the same length can be used to correspondingly improve the payload capacity, flight speed, or endurance of the UAV.

[0041] At the same time, such as Figure 3 As shown, the aforementioned physical boundary advantages, under the same weight constraint, translate into a multiple increase in cable laying distance. The fiber core load quotas for both are limited to identical fixed constants. The maximum allowable total length of wire laid out using the traditional method is: ; Based on the aforementioned weight reduction ratio, which frees up length accommodation space, the maximum permissible total wire length in this embodiment is... Satisfying the formula: ; Following the above application example, if the fiber optic core payload quota The total length of the wire laid out in the traditional method is fixed at 270 g. Based on the physical correspondence of longer length for the same weight, the maximum permissible total length of wire laid out in this embodiment is... The range has been extended to 27.77 km to 29.41 km. Its range gain factor... Satisfy the formula for extended gain of wire laying: ; Based on quartz fill factor With the boundary condition of 34% to 36%, the calculated length expansion ratio is 2.77 to 2.94 times, which multiplies the allowable operating radius and safe depth of the UAV without changing the total weight of the spool.

[0042] V. Verification of Communication Efficiency Improvement like Figure 4 As shown, the system architecture is based on a hollow air core structure, which significantly reduces the limitation imposed by the solid quartz matrix on the propagation speed of light signals. To evaluate the dynamic advantages under long-distance accumulation conditions, this embodiment introduces a dynamic simulation observation range of 0–160 km. The physical parameters satisfy the following quantitative relationships: The optical signal transmission speed in a solid single-mode fiber satisfies: ; Among them, the speed of light in vacuum Approximately Refractive index of pure quartz glass matrix The value is 1.44~1.45, calculated as follows: Corresponding to to In this embodiment, the optical signal velocity in the hollow anti-resonant fiber satisfies: ; air refractive index The value is 1.00, and the calculation yields... Corresponding to .

[0043] Therefore, the signal delay reduction ratio of hollow-core anti-resonant fiber compared to solid-core single-mode fiber is... satisfy: ; Calculations show that the signal delay reduction ratio is... The value range is 30% to 32%. Furthermore, a communication efficiency multiplication factor is defined. Satisfy the following formula: ; The communication efficiency multiplier was calculated. The corresponding value range is 1.44~1.45.

[0044] Table 1 presents the time delay comparison data of hollow anti-resonant fiber and solid single-mode fiber at different transmission distances: Table 1 Comparison of Fiber Optic Transmission Delay

[0045] Analysis of the above data shows that as the transmission distance increases linearly, the cumulative delay of solid single-mode optical fiber deteriorates drastically due to the high refractive index medium. However, by eliminating kilometer-level transmission lag, this invention can significantly reduce the cumulative communication delay during long-distance transmission of 160 km, thereby greatly improving the real-time control communication efficiency and high-definition image transmission response speed of UAV 1 compared to the traditional architecture.

[0046] VI. Communication Methods and Procedures The UAV communication method based on hollow optical fiber provided in this embodiment includes four stages in its complete process: pre-flight preparation, takeoff and dynamic cable laying, communication process, and landing and recovery.

[0047] (a) Pre-flight preparations Before takeoff, the operator neatly winds a pre-set length of hollow-core optical fiber 5 onto the storage spool 4. One end of the hollow-core optical fiber 5 is pre-leaded from the storage spool 4 and connected to the first single-fiber bidirectional optical module 2 via the mode field adapter 3; the other end is pre-leaded from the storage spool 4 and connected to the optical interconnect component 6 of the ground control station 9, completing the full-link connection before takeoff. At the same time, the first single-fiber bidirectional optical module 2 and the second single-fiber bidirectional optical module 8 are initialized and configured to match their operating wavelengths, establishing the basic parameters for the bidirectional communication link.

[0048] (ii) Takeoff and dynamic line setting After takeoff, UAV 1 flies forward, and the cable reel 4 passively rotates as UAV 1 moves forward, simultaneously releasing the hollow optical fiber 5 wound on it. As UAV 1 continues to fly forward, the hollow optical fiber 5 is gradually released from the cable reel 4, forming a dynamically extending physical optical channel between UAV 1 and ground control station 9. During this process, the cable release speed of the cable reel 4 is dynamically balanced with the flight speed of UAV 1 to ensure that the hollow optical fiber 5 is in a moderately tensioned state, avoiding excessive slack or excessive tension on the fiber.

[0049] (III) Communication Process During the flight and cable laying of UAV 1, the first single-fiber bidirectional optical module 2 and the second single-fiber bidirectional optical module 8 simultaneously conduct full-duplex bidirectional communication through the physical optical channel formed by the same hollow optical fiber 5: Downlink direction: The second single-fiber bidirectional optical module 8 converts downlink video signals and other data into optical signals, which are coupled into hollow fiber 5 via the ground-side solid single-mode fiber 7 and optical interconnect component 6. The signals are then transmitted to the UAV 1 via the hollow fiber 5, and coupled into the first single-fiber bidirectional optical module 2 via the mode field adapter 3. The first single-fiber bidirectional optical module 2 converts the optical signals into electrical signals for use by the airborne equipment. Uplink direction: The first single-fiber bidirectional optical module 2 converts the uplink control command into an optical signal, which is coupled into the hollow fiber 5 through the mode field adapter 3. The signal is then transmitted to the ground control station 9 through the hollow fiber 5, and then coupled into the second single-fiber bidirectional optical module 8 through the optical interconnect component 6 and the ground solid single-mode fiber 7. The second single-fiber bidirectional optical module 8 converts the optical signal into an electrical signal for use by the ground operators.

[0050] The optical signals in the two directions occupy different operating wavelengths and can be transmitted simultaneously in the same hollow optical fiber 5 without interfering with each other.

[0051] (iv) Landing and Recovery After the mission is completed, UAV 1 returns and lands. The cable reel 4 rotates in the opposite direction to rewind and store the hollow fiber 5. During the recovery process, the cable recovery speed must be controlled to match the landing speed of UAV 1 to avoid excessive stress or abnormal bending of the fiber. After the hollow fiber 5 is completely recovered, the connection at the ground control station 9 is disconnected, and the cable reel 4 and the hollow fiber 5 are properly stored for future use.

[0052] In summary, this invention introduces hollow-core anti-resonant optical fiber as the physical layer transmission medium in the UAV communication system, combined with an asymmetric optical path coupling layout (using a mode field adapter for all-fiber fusion splicing at the sky end and optical interconnect components for non-contact spatial optical coupling at the ground end). This achieves lightweighting of the fiber matrix to release axial weight quotas under the same length, significantly expands the allowable operating radius under the same weight conditions, and greatly reduces the cumulative transmission delay of optical signals by utilizing the air medium within the fiber, thus significantly improving communication efficiency.

[0053] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A UAV communication system based on hollow-core optical fiber, characterized in that, include: The drone is equipped with a first single-fiber bidirectional optical module. The ground control station is equipped with a second single-fiber bidirectional optical module. A wire storage spool, mounted on the UAV, is used to wind and release hollow optical fibers; One end of the hollow optical fiber extends through the storage spool into the UAV and is optically connected to the first single-fiber bidirectional optical module; the other end of the hollow optical fiber extends into the ground control station and is optically connected to the second single-fiber bidirectional optical module. The first single-fiber bidirectional optical module and the second single-fiber bidirectional optical module have complementary wavelengths and form a physical optical channel for simultaneous transmission of uplink control commands and downlink video signals through the same hollow optical fiber.

2. The system according to claim 1, characterized in that, The hollow optical fiber is a hollow anti-resonant optical fiber, which has an anti-resonant microstructure formed by multiple layers of thin-walled quartz capillaries surrounding a hollow air core.

3. The system according to claim 2, characterized in that, The quartz filling factor f of the hollow optical fiber ranges from 34% to 36%. The quartz filling factor f is defined as the ratio of the cross-sectional area of ​​the quartz material in the hollow optical fiber to the cross-sectional area of ​​the quartz matrix in a solid single-mode optical fiber with the same cladding outer diameter.

4. The system according to claim 1, characterized in that, The UAV is also equipped with a mode field adapter, and the hollow fiber is optically connected to the first single-fiber bidirectional optical module through the mode field adapter; the mode field adapter is used to adapt the mode field of the optical signal output by the first single-fiber bidirectional optical module to the hollow fiber.

5. The system according to claim 4, characterized in that, The mode field adapter is a section of transition fiber, and the end of the transition fiber has a mode field transition structure. The output end face of the mode field transition structure is directly fused and solidified with the light-incident end face of the hollow fiber.

6. The system according to claim 5, characterized in that, The mold field transition structure is one of the following: a reverse tapered structure, a thermo-expanded core structure, or a composite structure of tapered and thermo-expanded core.

7. The system according to claim 5, characterized in that, The transition fiber is a solid single-mode fiber.

8. The system according to claim 1, characterized in that, The ground control station is also equipped with an optical interconnect component, and the other end of the hollow fiber is optically connected to the optical interconnect component; the optical interconnect component is connected to the second single-fiber bidirectional optical module via a section of ground-end solid single-mode fiber.

9. The system according to claim 8, characterized in that, The optical interconnect component is a beam-expanding fiber connector, which includes a pair of lenses for expanding and refocusing the optical signal emitted from the end face of the hollow fiber, and then coupling it into the solid single-mode fiber at the ground end.

10. A UAV communication method based on hollow-core optical fiber, characterized in that, The method includes: When the UAV is in flight and releases the hollow fiber from the storage spool configured on the UAV, the first single-fiber bidirectional optical module configured in the UAV and the second single-fiber bidirectional optical module configured in the ground control station simultaneously transmit uplink control commands and downlink video signals bidirectionally through the hollow fiber.

Images