Real-time light intensity stabilization device and method, quantum key distribution system and its transmitter

Abstract

This application provides a real-time light intensity stabilization device and method, a quantum key distribution system and its transmitter, wherein the real-time light intensity stabilization device is applied to the transmitter of the quantum key distribution system. The real-time light intensity stabilization device includes a real-time stabilization module, a calibration module and a control module. The real-time stabilization module performs a first attenuation on the pulsed laser and outputs a first light intensity laser within a preset range, maintaining it at the first light intensity. After the first attenuation, the first light intensity laser is still strong light, that is, the strong light intensity is maintained. By detecting the strong light, the detection accuracy can be relatively improved. The calibration module is used for a second attenuation, attenuating the strong light laser of the first light intensity to a weak light laser of the second light intensity. The calibration module is also used to calibrate its own inherent attenuation at a preset time to take into account the influence of the aging of optical components on the inherent attenuation after long-term operation of the device, thereby ensuring the accuracy of the inherent attenuation.

Description

Technical Field

[0001] This invention relates to the field of communication technology, and in particular to a real-time light intensity stabilization device and method, a quantum key distribution system and its transmitter. Background Technology

[0002] Quantum key distribution (QKD) systems, to ensure information security, should theoretically use a single-photon source for key distribution. However, an ideal single-photon source does not exist in reality. Therefore, in practice, weakly coherent laser pulses with strong attenuation are typically used to simulate a single-photon source. During quantum key distribution transmission, fluctuations in light intensity can provide opportunities for attackers. For security reasons, the output light intensity at the transmitter of a QKD system needs to be maintained within a specific range.

[0003] In order to keep the output light intensity of the QKD system transmitter within a specific range, it is necessary to monitor and control the output light intensity and stabilize it.

[0004] However, the existing methods for maintaining stable light intensity at the output have significant errors. Summary of the Invention

[0005] In view of this, the present invention provides a real-time light intensity stabilization device and method, a quantum key distribution system and its transmitter, to solve the problem of large errors in the existing light intensity stabilization methods.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A real-time light intensity stabilization device is used at the transmitter of a quantum key distribution system; the real-time light intensity stabilization device includes: a real-time stabilization module, a calibration module, and a control module;

[0008] The real-time stabilization module is used to connect to the light source of the quantum key distribution system, receive the pulsed laser emitted by the light source, and output a first intensity laser within a preset range after attenuating the pulsed laser.

[0009] The input of the calibration module is connected to the output of the real-time stabilization module. The calibration module is used to calibrate its own inherent attenuation and attenuate the first intensity laser before outputting the second intensity laser. The second intensity laser is used as the output light of the transmitter of the quantum key distribution system.

[0010] A control module, which is connected to the real-time stabilization module and the calibration module respectively, is used to control the output of the real-time stabilization module to maintain a first light intensity when the quantum key distribution system is working normally, and to calibrate the inherent attenuation of the calibration module at a preset time.

[0011] Preferably, the real-time stabilization module includes a first adjustable attenuation unit, a first optical beam splitter, and a first optical power detection unit;

[0012] The input terminal of the first adjustable attenuation unit is connected to the light source of the quantum key distribution system, receives the pulsed laser emitted by the light source, attenuates the pulsed laser, and outputs the first intensity laser.

[0013] The first optical beam splitter splits the first high-intensity laser into at least a first beam and a second beam, wherein the first beam is transmitted to the calibration module;

[0014] The first optical power detection unit receives the second beam and performs light intensity detection on the second beam, and transmits the detected light intensity of the first light intensity laser to the control module;

[0015] The control module calculates a first compensation attenuation value based on the light intensity of the first high-intensity laser and feeds the first compensation attenuation value back to the first adjustable attenuation unit to maintain the output of the first high-intensity laser by the real-time stabilization module.

[0016] Preferably, the calibration module includes a second adjustable attenuation unit, a second optical beam splitter, and a second optical power detection unit;

[0017] The input terminal of the second adjustable attenuation unit is used to receive the first beam and attenuate the first beam before outputting the second intensity laser.

[0018] The second optical beam splitter splits the second high-intensity laser into at least a third beam and a fourth beam, wherein the third beam serves as the output light of the transmitter of the quantum key distribution system;

[0019] The second optical power detection unit receives the fourth beam and performs light intensity detection on the fourth beam, and transmits the detected light intensity of the second light intensity laser to the control module;

[0020] The control module calculates the second compensation attenuation value based on the light intensity of the second intensity laser, and feeds the second compensation attenuation value back to the second adjustable attenuation unit to calibrate the inherent attenuation value of the calibration module.

[0021] This invention also provides a method for real-time light intensity stabilization, applied in the aforementioned real-time light intensity stabilization device; the method for real-time light intensity stabilization includes:

[0022] The real-time stabilization module receives the pulsed laser emitted by the light source, attenuates the pulsed laser, and outputs a first intensity laser within a preset range.

[0023] The calibration module calibrates its own inherent attenuation and attenuates the first intensity laser before outputting a second intensity laser, which serves as the output light of the quantum key distribution system's transmitter.

[0024] When the quantum key distribution system is working normally, the control module controls the output of the real-time stabilization module to maintain the first light intensity, and at a preset time, calibrates the inherent attenuation of the calibration module so that the calibration module outputs the second light intensity laser.

[0025] Preferably, in the above-described real-time light intensity stabilization device, before the real-time stabilization module receives the pulsed laser emitted by the light source and outputs a first intensity laser within a preset range after attenuating the pulsed laser, the real-time stabilization method further includes:

[0026] Set the attenuation value of the first adjustable attenuation unit;

[0027] The inherent attenuation value of the measurement calibration module;

[0028] Set the attenuation value of the second adjustable attenuation unit.

[0029] Preferably, setting the attenuation value of the first adjustable attenuation unit specifically includes:

[0030] Acquire the pulsed laser emitted by the light source;

[0031] Based on the pulsed laser intensity and the detection accuracy of the first optical power detection unit, the attenuation value of the first adjustable attenuation unit is set.

[0032] Preferably, the inherent attenuation value of the measurement calibration module specifically includes:

[0033] Determine whether the preset time has been reached;

[0034] If so, set the attenuation value of the second adjustable attenuation unit to 0;

[0035] Acquire the calibration light emitted by the light source;

[0036] The light intensity of the second beam and the light intensity of the fourth beam are obtained;

[0037] The inherent attenuation value of the calibration module is obtained by subtracting the light intensity of the second beam from the light intensity of the fourth beam.

[0038] If not, the real-time stabilization module receives the pulsed laser emitted by the light source, attenuates the pulsed laser, and outputs a first intensity laser within a preset range.

[0039] Preferably, setting the attenuation value of the second adjustable attenuation unit specifically includes:

[0040] The attenuation value of the second adjustable attenuation unit is set according to the light intensity of the second beam, the inherent attenuation value of the calibration module, and the target output light intensity of the quantum key distribution system transmitter.

[0041] Based on the same inventive concept, the present invention also provides a transmitter for use in a quantum key distribution system, the transmitter comprising:

[0042] Real-time stabilization device for light source and light intensity;

[0043] The light source is used to emit pulsed laser light;

[0044] The real-time light intensity stabilization device receives and stabilizes the pulsed laser, so that the laser light intensity output by the real-time light intensity stabilization device is the target output light intensity of the transmitter of the quantum key distribution system.

[0045] The light intensity real-time stabilization device is the light intensity real-time stabilization device described above.

[0046] Preferably, the light source includes a laser and a modulation unit;

[0047] The modulation unit is used to modulate the phase and / or polarization state of the pulsed laser.

[0048] The present invention also provides a quantum key distribution system, comprising:

[0049] Transmitter and receiver;

[0050] The transmitter is the transmitter described above.

[0051] As can be seen from the above technical solutions, the real-time light intensity stabilization device and method, quantum key distribution system and its transmitter provided by the present invention, wherein the real-time light intensity stabilization device is applied to the transmitter of the quantum key distribution system, the real-time light intensity stabilization device includes a real-time stabilization module, a calibration module and a control module. The real-time stabilization module performs a first attenuation on the pulsed laser and outputs a first light intensity laser within a preset range, maintaining it at the first light intensity. After the first attenuation, the first light intensity laser is still strong light, that is, the strong light intensity is maintained. By detecting the strong light, the detection accuracy can be relatively improved. The calibration module is used for a second attenuation, attenuating the strong light laser of the first light intensity to a weak light laser of the second light intensity. The calibration module is also used to calibrate its own inherent attenuation at a preset time to take into account the influence of the aging of optical components on the inherent attenuation after long-term operation of the device, thereby ensuring the accuracy of the inherent attenuation. That is, the real-time light intensity stabilization device provided by the present invention achieves the attenuation of strong light to weak light through two attenuations, which serves as the output light of the transmitter.

[0052] Furthermore, in the process of attenuating the pulsed laser as strong light to the first intensity laser as strong light, the detection accuracy is improved by detecting the strong light and maintaining stability in real time compared to detecting the weak light. In the process of attenuating the first intensity laser as strong light to the second intensity laser as weak light, the inherent attenuation calibration of the calibration module is performed at a preset time. The influence of the aging of optical components on the inherent attenuation is taken as a factor that generates error, so as to ensure the accuracy of the second attenuation. This ensures that the output second intensity laser is the required output light intensity of the transmitter and remains stable, reducing the stabilization error and ensuring the accuracy of the output light intensity. Attached Figure Description

[0053] 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 embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0054] Figure 1 This is a schematic diagram of a real-time light intensity stabilization device provided in an embodiment of the present invention;

[0055] Figure 2 This is a schematic diagram of the specific structure of a real-time light intensity stabilization device provided in an embodiment of the present invention;

[0056] Figure 3 This is a schematic diagram of a real-time light intensity stabilization method provided in an embodiment of the present invention;

[0057] Figure 4 A detailed flowchart of a real-time light intensity stabilization method provided in an embodiment of the present invention;

[0058] Figure 5 This is a schematic diagram of the transmitter structure provided in an embodiment of the present invention;

[0059] Figure 6 This is a schematic diagram of a quantum key distribution system provided in an embodiment of the present invention. Detailed Implementation

[0060] As described in the background section, the existing methods for maintaining stable output light intensity have significant errors.

[0061] The inventors discovered that the root cause of the above phenomenon is that, since there are multiple optical devices in the optical path of the transmitter of the quantum key distribution system, the insertion loss of each device will inevitably be affected by environmental factors such as high and low temperatures, resulting in large fluctuations in the output light. This may cause the intensity of the output light at the transmitter of the QKD system to exceed the safety threshold range, posing a safety hazard to the QKD system.

[0062] Moreover, the single-photon level light intensity required for normal operation of the existing QKD system is relatively weak, and the detection accuracy of the light intensity monitoring unit decreases as the light intensity weakens. Therefore, it is impossible to guarantee accurate measurement of the light intensity of weak light, resulting in a large error in the existing method of monitoring and stabilizing the light intensity of weak light after strong attenuation.

[0063] Moreover, the existing technology only achieves single-time output light intensity stabilization through light intensity detection, without taking into account the output light intensity fluctuations caused by factors such as device aging and external ambient temperature after the QKD has been working for a period of time. This also results in a large error in the output light intensity stabilization method.

[0064] Based on this, the present invention provides a real-time light intensity stabilization device for use at the transmitter of a quantum key distribution system; the real-time light intensity stabilization device includes: a real-time stabilization module, a calibration module, and a control module;

[0065] The real-time stabilization module is used to connect to the light source of the quantum key distribution system, receive the pulsed laser emitted by the light source, and output a first intensity laser within a preset range after attenuating the pulsed laser.

[0066] The input of the calibration module is connected to the output of the real-time stabilization module. The calibration module is used to calibrate its own inherent attenuation and attenuate the first intensity laser before outputting the second intensity laser. The second intensity laser is used as the output light of the transmitter of the quantum key distribution system.

[0067] A control module, which is connected to the real-time stabilization module and the calibration module respectively, is used to control the output of the real-time stabilization module to maintain a first light intensity when the quantum key distribution system is working normally, and to calibrate the inherent attenuation of the calibration module at a preset time.

[0068] The real-time light intensity stabilization device provided by this invention is applied to the transmitter of a quantum key distribution system. The device includes a real-time stabilization module, a calibration module, and a control module. The real-time stabilization module performs a first attenuation on the pulsed laser and outputs a first-intensity laser within a preset range, maintaining this intensity. Even after the first attenuation, the first-intensity laser remains strong, thus maintaining its intensity. Detecting this strong light improves detection accuracy. The calibration module performs a second attenuation, reducing the strong laser of the first intensity to a weak laser of the second intensity. This calibration module also calibrates the device's inherent attenuation at preset times to account for the impact of optical component aging on inherent attenuation after long-term operation, ensuring the accuracy of the inherent attenuation. In other words, the real-time light intensity stabilization device provided by this invention achieves the attenuation of strong light to weak light through two attenuation stages, serving as the output light from the transmitter.

[0069] Furthermore, in the process of attenuating the pulsed laser as strong light to the first intensity laser as strong light, the detection accuracy is improved by detecting the strong light and maintaining stability in real time compared to detecting the weak light. In the process of attenuating the first intensity laser as strong light to the second intensity laser as weak light, the inherent attenuation calibration of the calibration module is performed at a preset time. The influence of the aging of optical components on the inherent attenuation is taken as a factor that generates error, so as to ensure the accuracy of the second attenuation. This ensures that the output second intensity laser is the required output light intensity of the transmitter and remains stable, reducing the stabilization error and ensuring the accuracy of the output light intensity.

[0070] 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.

[0071] Please see Figure 1 , Figure 1 This is a schematic diagram of a real-time light intensity stabilization device provided in an embodiment of the present invention; the real-time light intensity stabilization device in this embodiment is applied to the transmitter of a quantum key distribution system; the real-time light intensity stabilization device includes: a real-time stabilization module 1, a calibration module 2, and a control module 3;

[0072] The real-time stabilization module 1 is connected to the light source of the quantum key distribution system, receives the pulsed laser emitted by the light source, and outputs the first intensity laser I1 within a preset range after attenuating the pulsed laser.

[0073] The input of calibration module 2 is connected to the output of real-time stabilization module 1. Calibration module 2 is used to calibrate its own inherent attenuation and attenuate the first intensity laser I1 before outputting the second intensity laser I2. The second intensity laser I2 serves as the output light I2 of the quantum key distribution system transmitter. out ;

[0074] The control module 3 is connected to the real-time stabilization module 1 and the calibration module 2 respectively. It is used to control the output of the real-time stabilization module 1 to maintain the first light intensity when the quantum key distribution system is working normally, and to calibrate the inherent attenuation of the calibration module 2 at a preset time.

[0075] It should be noted that the real-time light intensity stabilization device provided in this embodiment achieves two light intensity attenuations. The first attenuation is to attenuate the pulsed laser to the first light intensity laser I1, and the second attenuation is to attenuate the first light intensity laser I1 to the second light intensity laser I2. In this embodiment, the first attenuation is an attenuation process from strong light to strong light, and the second attenuation is an attenuation process from strong light to weak light. That is, through two stages of attenuation, the single attenuation process in the prior art is achieved, realizing the attenuation of strong light to weak light, which is then emitted as the output light of the transmitting end.

[0076] This embodiment does not limit the specific structure of the real-time stabilization module and the calibration module; optional structures are as follows: Figure 2 As shown, Figure 2 This is a schematic diagram of a real-time light intensity stabilization device provided in an embodiment of the present invention. The real-time stabilization module 1 includes a first adjustable attenuation unit 11, a first optical beam splitter 12, and a first optical power detection unit 13. The input of the first adjustable attenuation unit 11 is connected to the light source of the quantum key distribution system, receives pulsed laser light emitted from the light source, attenuates the pulsed laser light, and outputs a first-intensity laser I1. The first optical beam splitter 12 splits the first-intensity laser light into at least a first beam and a second beam, wherein the first beam is transmitted to a calibration module. The first optical power detection unit 13 receives the second beam and performs light intensity detection on the second beam, transmitting the detected light intensity of the first-intensity laser light to a control module 3. The control module 3 calculates a first compensation attenuation value based on the light intensity of the first-intensity laser light and feeds back the first compensation attenuation value to the first adjustable attenuation unit 11 to maintain the output of the first-intensity laser I1 from the real-time stabilization module 1.

[0077] The calibration module 2 includes a second adjustable attenuation unit 21, a second optical beam splitter 22, and a second optical power detection unit 23. The input of the second adjustable attenuation unit 21 is used to receive the first beam and attenuate the first beam before outputting a second intensity laser I2. The second optical beam splitter 22 splits the second intensity laser into at least a third beam and a fourth beam, wherein the third beam serves as the output light I2 of the quantum key distribution system transmitter. The second optical power detection unit 23 receives the fourth beam and detects its intensity, transmitting the detected intensity of the second intensity laser to the control module. The control module calculates a second compensation attenuation value based on the intensity of the second intensity laser and feeds back the second compensation attenuation value to the second adjustable attenuation unit 23 to calibrate the inherent attenuation value of the calibration module.

[0078] In this embodiment, the specific parameters of each structure in the real-time stabilization module and calibration module are not limited. The detection accuracy of the first optical power detection unit 13 and the second optical power detection unit 23 may be the same or different. Since the fourth beam used by the second optical power detection unit is the light intensity after two attenuations, the corresponding light intensity is relatively weak. The detection accuracy of the optical power detection module decreases as the light intensity decreases. Therefore, in order to ensure that the detection accuracy of weak light also meets the requirements, in this embodiment, optionally, the detection accuracy of the second optical power detection unit is much greater than that of the first optical power detection unit.

[0079] In this embodiment, the specific light intensity values ​​of the first intensity laser I1 output by the real-time stabilization module and the second intensity laser I2 output by the calibration module are not limited. Since the first intensity laser is strong light and the second intensity laser is weak light, in this embodiment, the light intensity range of the first intensity laser I1 is -55dBm to -20dBm, and the light intensity range of the second intensity laser I2 is -90dBm to -80dBm.

[0080] Furthermore, in this embodiment, the first optical beamsplitter 12 and the second optical beamsplitter 22 can both be 1:1 beamsplitters, or both can be 1:n beamsplitters, or they can be beamsplitters with different numbers of beams split. The design can be tailored to actual needs, and this embodiment does not impose any limitations on this. For ease of explanation of the inventive concept of this embodiment, optionally, the first optical beamsplitter 12 and the second optical beamsplitter 22 are both 1:1 beamsplitters.

[0081] The real-time light intensity stabilization device provided by this invention is applied to the transmitter of a quantum key distribution system. The device includes a real-time stabilization module, a calibration module, and a control module. The real-time stabilization module performs a first attenuation on the pulsed laser and outputs a first-intensity laser within a preset range, maintaining this intensity. Even after the first attenuation, the first-intensity laser remains strong, thus maintaining its intensity. Detecting this strong light improves detection accuracy. The calibration module performs a second attenuation, reducing the strong laser of the first intensity to a weak laser of the second intensity. This calibration module also calibrates the device's inherent attenuation at preset times to account for the impact of optical component aging on inherent attenuation after long-term operation, ensuring the accuracy of the inherent attenuation. In other words, the real-time light intensity stabilization device provided by this invention achieves the attenuation of strong light to weak light through two attenuation stages, serving as the output light from the transmitter.

[0082] Furthermore, in the process of attenuating the pulsed laser as strong light to the first intensity laser as strong light, the detection accuracy is improved by detecting the strong light and maintaining stability in real time compared to detecting the weak light. In the process of attenuating the first intensity laser as strong light to the second intensity laser as weak light, the inherent attenuation calibration of the calibration module is performed at a preset time. The influence of the aging of optical components on the inherent attenuation is taken as a factor that generates error, so as to ensure the accuracy of the second attenuation. This ensures that the output second intensity laser is the required output light intensity of the transmitter and remains stable, reducing the stabilization error and ensuring the accuracy of the output light intensity.

[0083] Based on the real-time light intensity stabilization device in the above embodiments, this invention also provides a real-time light intensity stabilization method. Please refer to [link to relevant documentation]. Figure 3 , Figure 3 This is a schematic flowchart of a real-time light intensity stabilization method provided in an embodiment of the present invention; the real-time light intensity stabilization method includes:

[0084] S101: The real-time stabilization module receives the pulsed laser emitted by the light source, attenuates the pulsed laser, and outputs the first intensity laser within a preset range.

[0085] S102: The calibration module calibrates its own inherent attenuation and attenuates the first intensity laser before outputting the second intensity laser, which serves as the output light of the quantum key distribution system transmitter.

[0086] S103: When the quantum key distribution system is working normally, the control module controls the output of the real-time stabilization module to maintain the first light intensity, and at a preset time, calibrates the inherent attenuation of the calibration module so that the calibration module outputs a second light intensity laser.

[0087] It should be noted that the real-time light intensity stabilization method provided in this embodiment is performed in real time during the normal operation of the QKD system. Therefore, before the real-time light intensity stabilization method receives the pulsed laser emitted by the light source and outputs the first light intensity laser within the preset range after attenuating the pulsed laser, it usually includes: setting the attenuation value of the first adjustable attenuation unit; measuring the inherent attenuation value of the calibration module; and setting the attenuation value of the second adjustable attenuation unit.

[0088] Specifically, setting the attenuation value of the first adjustable attenuation unit includes: acquiring the pulsed laser emitted by the light source; and setting the attenuation value of the first adjustable attenuation unit based on the intensity of the pulsed laser and the detection accuracy of the first optical power detection unit.

[0089] The inherent attenuation value of the measurement calibration module specifically includes: determining whether a preset time has been reached; if so, setting the attenuation value of the second adjustable attenuation unit to 0; acquiring the calibration light emitted by the light source; obtaining the light intensity of the second beam and the light intensity of the fourth beam; subtracting the light intensity of the second beam from the light intensity of the fourth beam to obtain the inherent attenuation value of the calibration module; if not, returning to the real-time stabilization module to receive the pulsed laser emitted by the light source, and attenuating the pulsed laser before outputting the first intensity laser within the preset range.

[0090] Setting the attenuation value of the second adjustable attenuation unit specifically includes: setting the attenuation value of the second adjustable attenuation unit based on the light intensity of the second beam, the inherent attenuation value of the calibration module, and the target output light intensity of the quantum key distribution system transmitter.

[0091] The following describes the embodiments of the present invention. Figure 2 The real-time light intensity stabilization device is shown, and is illustrated using an example where both the first and second beamsplitters are 1:1 beamsplitters. Please refer to [link / reference]. Figure 4 , Figure 4 This is a flowchart illustrating a real-time light intensity stabilization method provided in an embodiment of the present invention; the real-time light intensity stabilization method includes:

[0092] S201: Obtain the light source intensity;

[0093] It should be noted that the light source is a light source formed by modulating the phase and / or polarization state of a laser through a modulation unit, and the intensity of the light source is the intensity of the light emitted by the laser after passing through the modulation unit.

[0094] S202: Set the attenuation value of the first adjustable attenuation unit;

[0095] According to the light source intensity I in and the lowest detectable light intensity I of the first optical power detection unit min Set the attenuation value A1 of the first adjustable attenuation unit. A1 needs to satisfy I in-A1>I min .

[0096] S203: Inherent attenuation of the measurement calibration module;

[0097] The attenuation value of the second adjustable attenuation unit 2 is set to 0, and the laser sends calibration light (intense light). The first optical power detection unit measures the first light intensity I1, and the second optical power detection unit measures the second light intensity I2. The difference between the two, ΔI = I1 – I2, is the inherent attenuation of the calibration module.

[0098] S204: Set the attenuation value of the second adjustable attenuation unit;

[0099] Based on the light intensity I1 measured by the first optical power detection unit, the inherent attenuation value of the calibration module, and the expected output light intensity I... out Set the attenuation value of the second adjustable attenuation unit to A2 = I1 - I out -ΔI.

[0100] The expected output light intensity mentioned in this embodiment is the output light intensity that the QKD system should use when it is working normally, that is, the target light intensity.

[0101] S205: The QKD system is working normally.

[0102] When the QKD system is working normally, the input light intensity of the calibration module remains constant, that is, the light intensity I1 measured by the first optical power detection unit is stable at a fixed value. If the light intensity I1 measured by the first optical power detection unit changes, the control module adjusts the attenuation value of the first adjustable attenuation unit to compensate for this change, so that I1 remains unchanged.

[0103] Simultaneously, a preset time is set. S206: Determine whether the preset time has been reached. If so, stop the normal operation of the QKD system and then return to S203 to remeasure the inherent attenuation of the calibration module. If the inherent attenuation has changed, adjust the attenuation value of the second adjustable attenuation unit so that the output of the calibration module is the target light intensity.

[0104] If the judgment result is negative, the process returns to the step of receiving the pulsed laser emitted by the light source in the real-time stabilization module, attenuating the pulsed laser, and outputting the first intensity laser within the preset range, that is, continuing to implement stabilization.

[0105] It should be noted that the specific length of the preset time is not limited in this embodiment. Due to the inherent attenuation of the calibration module, which is caused by the aging of components after long-term use, the preset time in this embodiment can be selected as more than 2 hours of normal operation of the QKD system. Furthermore, since frequent calibration can improve the accuracy of real-time stability maintenance, but leads to frequent switching of the QKD system between normal operation and shutdown, the preset time in this embodiment can be selected as one month, taking into account practical considerations.

[0106] More specifically, the light intensity I of the light source provided in this embodiment in = -10dBm; The attenuation value A1 of the first adjustable attenuation unit is 10dB;

[0107] The attenuation value of the second adjustable attenuation unit is set to 0, and the laser sends calibration light (intense light). The first light intensity I1 measured by the first optical power detection unit is -23dBm. Assuming that the second light intensity I2 measured by the second optical power detection unit is -28dBm, the inherent attenuation value of the calibration module is ΔI = I1 – I2 = 5dB.

[0108] Assuming the expected export light intensity I out = -85dBm; then set the attenuation value of the second adjustable attenuation unit to A2 = I1 - I out -ΔI=-23-(-85)-5=57dB.

[0109] The QKD system has started working normally.

[0110] Real-time stability maintenance:

[0111] When the QKD system is working normally, the first light intensity measured by the first optical power detection unit is kept at I1 = -23dBm. If the actual measured first light intensity is I1' = -25dBm, the control module reduces the attenuation value of the first adjustable attenuation unit by 2dB. Then the light intensity of the light output by the corresponding real-time stabilization module is restored to -25 + 2 = -23dB, which is to maintain the fixed value of the first light intensity I1.

[0112] As can be seen from the above-described real-time light intensity stabilization method, the real-time light intensity stabilization method in this embodiment of the invention can stabilize the output light of the transmitter in real time during the normal operation of the QKD system, so that the output light is maintained within a specific range, thereby improving the accuracy of stabilization and making the output light intensity more stable.

[0113] Based on the same inventive concept, this invention also provides a transmitter, please refer to [link to relevant documentation]. Figure 5 , Figure 5This is a schematic diagram of the transmitter structure provided in an embodiment of the present invention; the transmitter is applied in a quantum key distribution system, and the transmitter includes: a light source 10 and a real-time light intensity stabilization device 20;

[0114] The light source 10 is used to emit pulsed laser light; the real-time intensity stabilization device 20 receives the pulsed laser light and stabilizes it, so that the laser light intensity output by the real-time intensity stabilization device is the target output light intensity of the transmitter of the quantum key distribution system; the real-time intensity stabilization device is the same as the real-time intensity stabilization device in the above embodiment.

[0115] In this embodiment, the light source 10 includes a laser 101 and a modulation unit 102; the modulation unit 102 is used to modulate the phase and / or polarization state of the pulsed laser.

[0116] Because the transmitter includes a real-time light intensity stabilization device, it can maintain the output light intensity of the transmitter in a stable manner, improving the accuracy of the stabilization and making the output light intensity more stable.

[0117] Furthermore, based on the same inventive concept, such as Figure 6 As shown, Figure 6 This is a schematic diagram of a quantum key distribution system provided in an embodiment of the present invention; wherein, the new quantum key distribution system 100 includes: a transmitter 110 and a receiver 120; the transmitter 110 is the transmitter described in the above embodiment.

[0118] The quantum key distribution system provided in this embodiment includes the transmitter in the above embodiment. Due to the better stability of the output light, the light intensity of the output light of the QKD system transmitter is within the safe threshold range, thus avoiding security risks to the QKD system.

[0119] It should be noted that the various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0120] It should also be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that an article or apparatus comprising a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such an article or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the article or apparatus that includes the aforementioned element.

[0121] 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 real-time light intensity stabilization device, characterized in that, The transmitter for a quantum key distribution system; the real-time light intensity stabilization device includes: a real-time stabilization module, a calibration module, and a control module; The real-time stabilization module includes a first adjustable attenuation unit, which is connected to the light source of the quantum key distribution system, receives the pulsed laser emitted by the light source, attenuates the pulsed laser, and outputs a first intensity laser within a preset range, wherein the first intensity laser is strong light, and the first intensity I1 of the first intensity laser output from the real-time stabilization module is measured. The calibration module includes a second adjustable attenuation unit. The input of the calibration module is connected to the output of the real-time stabilization module. The calibration module is used to calibrate its own inherent attenuation and attenuate the first intensity laser before outputting a second intensity laser. The second intensity laser serves as the output light of the quantum key distribution system's transmitter. The calibration module is also configured to measure its inherent attenuation. Specifically, the attenuation value of the second adjustable attenuation unit is set to 0, and the second intensity I2 of the second intensity laser output from the calibration module is measured. The difference between the two intensities, ΔI = I1 - I2, is the inherent attenuation of the calibration module. The attenuation value A2 of the second adjustable attenuation unit is set to I1 - I2. out -ΔI, where I out The target light intensity when the quantum key distribution system is operating normally; A control module, which is connected to the real-time stabilization module and the calibration module respectively, is used to control the output of the real-time stabilization module to maintain a first light intensity when the quantum key distribution system is working normally, and to calibrate the inherent attenuation of the calibration module at a preset time.

2. The real-time light intensity stabilization device according to claim 1, characterized in that, The real-time stability module also includes a first optical beam splitter and a first optical power detection unit; The input terminal of the first adjustable attenuation unit is connected to the light source of the quantum key distribution system, receives the pulsed laser emitted by the light source, attenuates the pulsed laser, and outputs the first intensity laser. The first optical beam splitter splits the first high-intensity laser into at least a first beam and a second beam, wherein the first beam is transmitted to the calibration module; The first optical power detection unit receives the second beam and performs light intensity detection on the second beam, and transmits the detected light intensity of the first light intensity laser to the control module; The control module calculates a first compensation attenuation value based on the light intensity of the first high-intensity laser and feeds the first compensation attenuation value back to the first adjustable attenuation unit to maintain the output of the first high-intensity laser by the real-time stabilization module.

3. The real-time light intensity stabilization device according to claim 2, characterized in that, The calibration module also includes a second optical beam splitter and a second optical power detection unit; The input terminal of the second adjustable attenuation unit is used to receive the first beam and attenuate the first beam before outputting the second intensity laser. The second optical beam splitter splits the second high-intensity laser into at least a third beam and a fourth beam, wherein the third beam serves as the output light of the transmitter of the quantum key distribution system; The second optical power detection unit receives the fourth beam and performs light intensity detection on the fourth beam, and transmits the detected light intensity of the second light intensity laser to the control module; The control module calculates the second compensation attenuation value based on the light intensity of the second intensity laser, and feeds the second compensation attenuation value back to the second adjustable attenuation unit to calibrate the inherent attenuation value of the calibration module.

4. A method for real-time stabilization of light intensity, characterized in that, Applied to the real-time light intensity stabilization device according to any one of claims 1-3; The real-time light intensity stabilization method includes: The real-time stabilization module receives the pulsed laser emitted by the light source, attenuates the pulsed laser, and outputs a first intensity laser within a preset range. The calibration module calibrates its own inherent attenuation and attenuates the first intensity laser before outputting a second intensity laser, which serves as the output light of the quantum key distribution system's transmitter. When the quantum key distribution system is working normally, the control module controls the output of the real-time stabilization module to maintain the first light intensity, and at a preset time, calibrates the inherent attenuation of the calibration module so that the calibration module outputs the second light intensity laser.

5. The real-time light intensity stabilization method according to claim 4, characterized in that, The real-time intensity stabilization method further includes, before the real-time stabilization module receives the pulsed laser emitted by the light source and outputs a first intensity laser within a preset range after attenuating the pulsed laser: Set the attenuation value of the first adjustable attenuation unit; The inherent attenuation value of the measurement calibration module; Set the attenuation value of the second adjustable attenuation unit.

6. The real-time light intensity stabilization method according to claim 5, characterized in that, Setting the attenuation value of the first adjustable attenuation unit specifically includes: Acquire the pulsed laser emitted by the light source; Based on the pulsed laser intensity and the detection accuracy of the first optical power detection unit, the attenuation value of the first adjustable attenuation unit is set.

7. The real-time light intensity stabilization method according to claim 5, characterized in that, The inherent attenuation value of the measurement calibration module specifically includes: Determine whether the preset time has been reached; If so, set the attenuation value of the second adjustable attenuation unit to 0; Acquire the calibration light emitted by the light source; The light intensity of the second beam and the light intensity of the fourth beam are obtained; The inherent attenuation value of the calibration module is obtained by subtracting the light intensity of the second beam from the light intensity of the fourth beam. If not, the real-time stabilization module receives the pulsed laser emitted by the light source, attenuates the pulsed laser, and outputs a first intensity laser within a preset range.

8. The real-time light intensity stabilization method according to claim 7, characterized in that, Setting the attenuation value of the second adjustable attenuation unit specifically includes: The attenuation value of the second adjustable attenuation unit is set according to the light intensity of the second beam, the inherent attenuation value of the calibration module, and the target output light intensity of the quantum key distribution system transmitter.

9. A transmitter, characterized in that, In a quantum key distribution system, the transmitter includes: Real-time stabilization device for light source and light intensity; The light source is used to emit pulsed laser light; The real-time light intensity stabilization device receives and stabilizes the pulsed laser, so that the laser light intensity output by the real-time light intensity stabilization device is the target output light intensity of the transmitter of the quantum key distribution system. The real-time light intensity stabilization device is the real-time light intensity stabilization device according to any one of claims 1-3.

10. The transmitting end according to claim 9, characterized in that, The light source includes a laser and a modulation unit; The modulation unit is used to modulate the phase and / or polarization state of the pulsed laser.

11. A quantum key distribution system, characterized in that, include: Transmitter and receiver; The transmitting end is the transmitting end described in claim 9 or 10.

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