Coaxial adjustment system and method of quantum key distribution receiving system

Abstract

The invention discloses a coaxial adjustment system and method for a quantum key distribution receiving system, and the method comprises the steps: enabling fixed star light simulation parallel light as a light source to enter a rear light path module and a paraxial module, and displaying fixed star light spots in a first camera in the rear light path module and a second camera in the paraxial module respectively, the coaxiality deviation is calculated by calculating the light spot mass center of the fixed star light spot entering the second camera and the light spot mass center of the reverse beacon light entering the second camera, and the coaxiality deviation meets the design requirement by adjusting the position of a beacon light collimator of the paraxial module, so that the optical axes of the quantum light and the beacon light are coaxial; the method is suitable for external field coaxial adjustment of a satellite-ground quantum key distribution receiving system.

Description

Technical Field

[0001] The present invention relates to the field of satellite-to-ground optical communications, and in particular to a coaxial adjustment system and method for a quantum key distribution receiving system. Background Art

[0002] The statements in this section merely provide background information related to the present invention and do not necessarily constitute prior art.

[0003] In a satellite-to-ground quantum key distribution (QKD) receiving system, an optical path consisting of quantum light, beacon light, and laser communication light is required. Quantum light is generally a weakly coherent light source used to transmit photon signals; beacon light is a light source used to assist in establishing optical links; and laser communication light is a light source used for classical information exchange. Due to spectral isolation and other reasons, the beacon light and quantum light must be combined and split in free space, with their coaxial deviation maintained within tens of microradians.

[0004] When coaxial adjustment of equipment is required in the field, the telescope tube must be disassembled and assembled, then moved to the optical laboratory for adjustment. This requires manpower and carries risks during transportation. Furthermore, due to the long-term storage of the equipment in the field, the telescope tube can be affected by temperature and environmental factors, causing the coaxiality to fail to meet experimental requirements. Furthermore, the field equipment must be equipped with beam analyzers, collimators, and other laser devices of various wavelengths. Pre-setting an indoor environment for testing and adjustment consumes a large amount of hardware resources and the calibration process is cumbersome. Furthermore, returning the equipment to the factory results in poor timeliness in O&M. Summary of the Invention

[0005] To address the above issues, the present invention proposes a coaxial adjustment system and method for a quantum key distribution receiving system. This system and method utilize existing satellite-to-ground quantum key distribution equipment and starlight, without relying on additional hardware resources used in an indoor debugging environment. The coaxial adjustment of the beacon light and quantum light of the satellite-to-ground quantum key distribution receiving system is achieved, and is suitable for outdoor coaxial adjustment of the satellite-to-ground quantum key distribution receiving system.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] In a first aspect, the present invention provides a coaxial adjustment system for a quantum key distribution receiving system, comprising:

[0008] The telescope is used to receive starlight, converge the starlight, and send it to the rear optical path module;

[0009] The rear optical path module is used to receive the starlight after the beam is reduced and focused, and to display the first starlight spot;

[0010] The paraxial module includes a guide mirror provided on the paraxial side of the telescope, a beacon light collimator provided on the guide mirror, and a corner reflection prism provided at the light outlet of the beacon light collimator; the guide mirror is used to receive starlight and reflected beacon light emitted by the beacon light collimator and reflected by the corner reflection prism, and display a second starlight spot and the reflected beacon light spot;

[0011] A rotatable turntable for carrying the telescope and adjusting its attitude until the first starlight spot is located at a pre-calibrated calibration point;

[0012] The processor is used to record the position of the second starlight spot and the position of the reflected beacon light spot when the first starlight spot is located at a pre-calibrated calibration point, and determine the positional deviation of the two spot positions until the positional deviation is within a set range after adjusting the position of the beacon light collimator.

[0013] As an optional implementation, the rear optical path module includes a first camera, and the first camera is used to display the first star light spot.

[0014] As an optional embodiment, the corner reflection prism covers both the light outlet of the beacon light collimator and the guide mirror, so as to deflect the beacon light emitted from the beacon light collimator into the guide mirror.

[0015] As an optional embodiment, the paraxial module further includes a second camera disposed at the rear end of the guide mirror, and the second camera is used to display the second star light spot and the reflected beacon light spot.

[0016] As an optional implementation, when the beacon light collimator emits beacon light, the beacon light power is set to a minimum value, and the exposure and gain parameters of the second camera are adjusted to minimize the grayscale value of the reflected beacon light spot.

[0017] As an optional embodiment, when the guide mirror receives star light, the corner reflection prism is not provided, and the corner reflection prism is only provided when the beacon light collimator emits beacon light.

[0018] As an optional embodiment, it also includes a controller for controlling the rotatable turntable to adjust the azimuth and / or pitch angle of the telescope, so that the telescope and the paraxial module can receive starlight, and at the same time lock the position of the first starlight spot to a pre-calibrated calibration point.

[0019] As an optional implementation, the pre-calibrated calibration point is the centroid position coordinate of the receiving efficiency contour map corresponding to any one of the uplink laser communication light, the downlink laser communication light and the quantum light.

[0020] In a second aspect, the present invention provides a coaxial adjustment method for a quantum key distribution receiving system, using the system described in the first aspect, comprising:

[0021] Controlling the rotatable turntable to aim the telescope at a star, and causing the telescope and the paraxial module to receive starlight respectively, the telescope converging the starlight and sending it to the rear optical path module, and displaying a first starlight spot and a second starlight spot in the rear optical path module and the paraxial module respectively;

[0022] Lock the position of the first starlight spot to the pre-calibrated calibration point, and record the position of the second starlight spot at this time;

[0023] A corner reflector prism is set in front of the beacon light collimator and the guide mirror to reflect the beacon light emitted by the beacon light collimator back to the guide mirror, and the reflected beacon light spot is displayed and the position of the reflected beacon light spot is recorded;

[0024] The position deviation between the second star light spot and the reflected beacon light spot is calculated, and the position deviation is made within the set range by adjusting the position of the beacon light collimator.

[0025] In a third aspect, the present invention provides a quantum key distribution receiving system, which uses the system described in the first aspect or the method described in the second aspect to perform coaxial adjustment.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] The present invention proposes a coaxial adjustment system and method for a quantum key distribution receiving system. This system utilizes existing satellite-to-ground quantum key distribution equipment and starlight to achieve coaxial adjustment of the beacon light and quantum light of the satellite-to-ground quantum key distribution receiving system. Without relying on a beam analyzer and collimator used in an indoor debugging environment, the system can rapidly perform optical axis calibration, ensuring that the optical axes of the quantum light and the beacon light remain within tens of microradians. The system is suitable for outdoor coaxial adjustment of satellite-to-ground quantum key distribution receiving systems.

[0028] The present invention is time-effective and has high adjustment efficiency in an outdoor environment. During the implementation process, there is no need to disassemble and transport the telescope barrel, which saves manpower and time costs and reduces transportation risks. It is suitable for coaxial adjustment of various ground stations (fixed stations and mobile stations).

[0029] Advantages of additional aspects of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The accompanying drawings, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0031] Figure 1 This is a schematic diagram of the working principle of the satellite-to-ground quantum key distribution receiving system;

[0032] Figure 2 A schematic diagram of the structure of a coaxial adjustment system of a quantum key distribution receiving system provided in Example 1 of the present invention;

[0033] Figure 3 Schematic diagram of the paraxial module receiving starlight provided by Example 1 of the present invention;

[0034] Figure 4 Schematic diagram of the sidearm module receiving reflected beacon light provided by Example 1 of the present invention. DETAILED DESCRIPTION

[0035] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0036] It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present invention belongs.

[0037] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that the terms "include" and "comprise" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device comprising a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0038] In the absence of conflict, the embodiments of the present invention and the features thereof may be combined with each other.

[0039] Example 1

[0040] This embodiment provides a coaxial adjustment system for a quantum key distribution receiving system, including:

[0041] The telescope is used to receive starlight, converge the starlight, and send it to the rear optical path module;

[0042] The rear optical path module is used to receive the starlight after the beam is reduced and focused, and to display the first starlight spot;

[0043] The paraxial module includes a guide mirror provided on the paraxial side of the telescope, a beacon light collimator provided on the guide mirror, and a corner reflection prism provided at the light outlet of the beacon light collimator; the guide mirror is used to receive starlight and reflected beacon light emitted by the beacon light collimator and reflected by the corner reflection prism, and display a second starlight spot and the reflected beacon light spot;

[0044] A rotatable turntable for carrying the telescope and adjusting its attitude until the first starlight spot is located at a pre-calibrated calibration point;

[0045] The processor is used to record the position of the second starlight spot and the position of the reflected beacon light spot when the first starlight spot is located at a pre-calibrated calibration point, and determine the positional deviation of the two spot positions until the positional deviation is within a set range after adjusting the position of the beacon light collimator.

[0046] The satellite-to-ground quantum key distribution receiving system (or satellite-to-ground laser communication system) realizes the quantum key distribution function by receiving quantum light from the satellite payload. The working principle is as follows: Figure 1 As shown: When the satellite passes by, the sidearm module emits uplink beacon light to the payload, and at the same time, the main barrel of the telescope emits uplink laser communication light. After receiving the uplink beacon light, the payload transmits downlink beacon light (i.e., downlink laser communication light) and quantum light to the ground. At this time, the uplink laser communication light and downlink laser communication light links are established, and the main barrel realizes real-time quantum key distribution after receiving the quantum light.

[0047] Due to the reversibility of the optical path and the wide wavelength range of stellar emission, which can cover the system's required wavelengths and meet adjustment requirements, this embodiment uses star tracking to achieve the purpose of optical coaxial adjustment of the device in an outdoor environment. Starlight simulates parallel light as the light source and enters the rear optical path module and the sidearm module. The starlight spot is displayed in the first camera in the rear optical path module and the second camera in the sidearm module, respectively. The coaxiality deviation is calculated by calculating the spot center of mass of the starlight spot entering the second camera and the spot center of mass of the reflected beacon light entering the second camera. The coaxiality deviation is then adjusted to meet the design requirements by adjusting the position of the beacon light collimator in the sidearm module, thereby ensuring that the quantum light and the beacon light optical axis are coaxial.

[0048] like Figure 2 As shown, the coaxial adjustment system specifically includes a telescope 1, a rear optical path module 2, a rangefinder module 3, a dual-axis turntable 4, a tracking and aiming control chassis 5, and a tracking and aiming control software 6. The functions of each part are as follows:

[0049] (1) Telescope 1, including a main lens barrel, a secondary lens and an eyepiece are arranged in the main lens barrel, and the secondary lens and the eyepiece are located on the same axis; Telescope 1 is used to track stars and receive starlight, and the received starlight is focused to the eyepiece through the eyepiece and the secondary lens, and then sent to the rear optical path module 2.

[0050] (2) The rear optical path module 2 receives the starlight from the telescope 1 after the starlight is converged and displayed in the first camera (such as a precision camera) display area.

[0051] (3) a paraxial module 3, mounted on the main barrel of the telescope 1, comprising a guide mirror disposed on the main barrel of the telescope, a second camera (e.g., a coarse camera) disposed at the rear end of the guide mirror, a beacon light collimator disposed above the guide mirror, and a corner reflector prism disposed at the light outlet of the beacon light collimator;

[0052] The guide mirror is used to receive starlight and display a second starlight spot in the display area of ​​the second camera;

[0053] The beacon light collimator is used to emit beacon light, and the corner reflection prism is used to reflect the beacon light emitted by the beacon light collimator into the guide mirror, so as to display the reflected beacon light spot on the second camera;

[0054] Among them, when the guide mirror receives star light, no corner reflection prism is set, such as Figure 3 As shown;

[0055] When the beacon light collimator emits beacon light, a corner reflection prism is set at the light outlet of the beacon light collimator, and the corner reflection prism covers the light outlet of the beacon light collimator and the guide mirror at the same time to refract the beacon light into the guide mirror. Figure 4 shown.

[0056] Specifically, after locking the position of the first star light spot to the pre-calibrated calibration point and recording the position of the second star light spot at this time, place the corner reflection prism in front of the beacon light collimator and the guide mirror, set the beacon light power to the minimum value, and use the corner reflection prism at the light outlet of the beacon light collimator to reflect the beacon light into the second camera of the rangefinder module 3. At the same time, adjust the exposure and gain parameters of the second camera to minimize the grayscale value of the reflected beacon light spot, that is, make the light spot in the second camera as gray and dark as possible, and the light spot is round and has no burrs; if the reflected beacon light spot is not within the field of view of the second camera, it is necessary to manually adjust the position of the beacon light collimator to make the reflected beacon light spot enter the field of view of the second camera.

[0057] (4) A dual-axis turntable 4 is used to carry the telescope 1 and the rear optical path module 2, and is combined with a tracking and aiming control chassis 5 to control and adjust the azimuth and / or elevation angle of the telescope 1.

[0058] The dual-axis turntable 4 is a rotatable turntable. In other embodiments, the rotatable turntable may be other devices capable of controlling the multi-degree-of-freedom movement of the telescope, and is not limited to the dual-axis turntable.

[0059] (5) The tracking and aiming control box 5 is used to drive the dual-axis turntable 4 and receive tracking instructions from the tracking and aiming control software 6. By controlling the dual-axis turntable 4, the azimuth and / or pitch angle of the telescope 1 can be controlled so that the telescope 1 points to a star, and the telescope 1 and the rangefinder module 3 can receive star light. At the same time, the tracking and aiming control software 6 is used to lock the light spot and lock the position of the first star light spot to a pre-calibrated calibration point.

[0060] Among them, the pre-calibrated calibration point is: in an indoor environment, a collimator is used to emit parallel light to the system, and a calibration point is pre-calibrated. For example, the calibration point can be the centroid position coordinate of the receiving efficiency contour map corresponding to any one of the indoor uplink laser communication light, downlink laser communication light and quantum light.

[0061] In this embodiment, the position of the beacon light collimator of the paraxial module is manually adjusted to ensure that the coaxiality of the paraxial module and the telescope meets the requirements of the field test, thereby making the quantum light and the beacon light optical axis coaxial.

[0062] Example 2

[0063] This embodiment provides a coaxial adjustment method for a quantum key distribution receiving system, using the coaxial adjustment system for the quantum key distribution receiving system described in Example 1, including:

[0064] (1) Correct connection Figure 2 Then power on each device to confirm that it is working properly.

[0065] (2) Use the tracking and aiming control box 5 to control the dual-axis turntable 4 so that the telescope 1 points to a star. When the starlight spot appears in the display area of ​​the second camera of the side-view module 3 and the first camera of the rear optical path module 2, use the tracking and aiming control software 6 to lock the spot, lock the position of the starlight spot in the first camera to the pre-calibrated calibration point, and record the starlight spot position (x1, y1) in the second camera at this time.

[0066] Among them, the pre-calibrated calibration point is: in an indoor environment, a collimator is used to emit parallel light to the system, and a calibration point is pre-calibrated. For example, the calibration point can be the centroid position coordinate of the receiving efficiency contour map corresponding to any one of the indoor uplink laser communication light, downlink laser communication light and quantum light.

[0067] (3) Figure 4As shown, place the corner reflection prism in front of the beacon light collimator and the guide mirror, open the beacon light chassis (not shown in the figure), set the beacon light power to the minimum value, and the beacon light is emitted through the beacon light collimator through the beacon light pigtail. Use the corner reflection prism at the light outlet of the beacon light collimator to reflect the beacon light into the second camera of the paraxial module 3 (if the reflected beacon light spot is not within the field of view of the second camera, it is necessary to manually adjust the position of the beacon light collimator so that the reflected beacon light spot enters the field of view of the second camera), adjust the exposure and gain parameters of the second camera to minimize the grayscale value of the reflected beacon light spot (adjust the exposure and gain of the second camera to make the light spot in the second camera as gray and dark as possible, and the light spot is round and has no burrs), and record the reflected beacon light spot position (x2, y2) of the second camera display area at this time.

[0068] (4) Calculate the deviation between the second starlight spot position (x1, y1) in the second camera and the reflected beacon light spot position (x2, y2): |x1-x2| and |y1-y2|.

[0069] (5) By manually adjusting the position of the beacon light collimator, the deviation between the spot position of the beacon light after it is reflected into the second camera and the spot position of the second star light is within a set range; for example, within 5 pixels, that is, |x1-x2|≤5, |y1-y2|≤5.

[0070] (6) After the adjustment is completed, the beacon light collimator is reinforced to complete the coaxial adjustment of the beacon light and the quantum light.

[0071] Although the above describes the specific embodiments of the present invention in conjunction with the accompanying drawings, it is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art on the basis of the technical solution of the present invention without any creative work are still within the scope of protection of the present invention.

Claims

1. A coaxial adjustment system for a quantum key distribution receiving system, characterized in that: include: The telescope is used to receive starlight, converge the starlight, and send it to the rear optical path module; The rear optical path module is used to receive the starlight after the beam is reduced and focused, and to display the first starlight spot; The paraxial module includes a guide mirror provided on the paraxial side of the telescope, a beacon light collimator provided on the guide mirror, and a corner reflection prism provided at the light outlet of the beacon light collimator; the guide mirror is used to receive starlight and reflected beacon light emitted by the beacon light collimator and reflected by the corner reflection prism, and display a second starlight spot and the reflected beacon light spot; A rotatable turntable for carrying the telescope and adjusting its attitude until the first starlight spot is located at a pre-calibrated calibration point; The processor is used to record the position of the second starlight spot and the position of the reflected beacon light spot when the first starlight spot is located at a pre-calibrated calibration point, and determine the positional deviation of the two spot positions until the positional deviation is within a set range after adjusting the position of the beacon light collimator.

2. The coaxial adjustment system of a quantum key distribution receiving system according to claim 1, characterized in that: The rear optical path module includes a first camera, and the first camera is used to display a first star light spot.

3. The coaxial adjustment system of a quantum key distribution receiving system according to claim 1, characterized in that: The corner reflection prism covers the light outlet of the beacon light collimator and the guide mirror at the same time, so as to refract and reflect the beacon light emitted by the beacon light collimator into the guide mirror.

4. The coaxial adjustment system of a quantum key distribution receiving system according to claim 3, characterized in that: The paraxial module also includes a second camera arranged at the rear end of the guide mirror, and the second camera is used to display the second star light spot and the reflected beacon light spot.

5. The coaxial adjustment system of a quantum key distribution receiving system according to claim 4, characterized in that: When the beacon light collimator emits beacon light, the beacon light power is set to the minimum value, and the exposure and gain parameters of the second camera are adjusted to minimize the grayscale value of the reflected beacon light spot.

6. The coaxial adjustment system of a quantum key distribution receiving system according to claim 3, characterized in that: When the guide mirror receives star light, the corner reflection prism is not provided. The corner reflection prism is provided only when the beacon light collimator emits beacon light.

7. The coaxial adjustment system of a quantum key distribution receiving system according to claim 1, characterized in that: It also includes a controller for controlling the rotatable turntable to adjust the azimuth and / or pitch angle of the telescope so that the telescope and the paraxial module can receive starlight, and at the same time lock the position of the first starlight spot to a pre-calibrated calibration point.

8. The coaxial adjustment system of a quantum key distribution receiving system according to claim 1, characterized in that: The pre-calibrated calibration point is the coordinate of the centroid position of the receiving efficiency contour map corresponding to any one of the uplink laser communication light, the downlink laser communication light and the quantum light.

9. A coaxial adjustment method for a quantum key distribution receiving system, characterized in that: A coaxial adjustment system for a quantum key distribution receiving system according to any one of claims 1 to 8, comprising: Controlling the rotatable turntable to aim the telescope at a star, and causing the telescope and the paraxial module to receive starlight respectively, the telescope converging the starlight and sending it to the rear optical path module, and displaying a first starlight spot and a second starlight spot in the rear optical path module and the paraxial module respectively; Lock the position of the first starlight spot to the pre-calibrated calibration point, and record the position of the second starlight spot at this time; A corner reflector prism is set in front of the beacon light collimator and the guide mirror to reflect the beacon light emitted by the beacon light collimator back to the guide mirror, and the reflected beacon light spot is displayed and the position of the reflected beacon light spot is recorded; The position deviation between the second star light spot and the reflected beacon light spot is calculated, and the position deviation is made within the set range by adjusting the position of the beacon light collimator.

10. A quantum key distribution receiving system, characterized in that: Coaxial adjustment is performed using the system of any one of claims 1 to 8 or the method of claim 9.

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