Apparatus and method for quantum signal and classical signal multiplexed optical fiber transmission

Abstract

This invention discloses an apparatus and method for transmitting quantum and classical signals via multiplexed optical fiber. By setting an adaptive optical intensity adjustment device that communicates with a QKD receiver terminal between the classical signal input module and the first wavelength division multiplexer, the adaptive optical intensity adjustment device automatically adjusts the attenuation coefficient to attenuate the classical signal based on the noise feedback information from the QKD receiver terminal. This achieves adjustment of the classical signal according to the actual network conditions, solving the technical problem that existing methods for transmitting quantum and classical signals via the same optical fiber cannot adjust the optical intensity of the classical signal to adapt to different network environments and have a limited scope of application.

Description

Technical Field

[0001] This invention relates to the field of quantum secure communication, and more particularly to an apparatus and method for transmitting quantum signals and classical signals multiplexed in optical fiber. Background Technology

[0002] Cryptography is a fundamental means of protecting information security. It is a technology that allows information exchange between A and B without the knowledge of unauthorized third parties. In modern secure communication technology, assuming that the sender Alice and the receiver Bob want to communicate securely, Alice uses an encryption key K to transform the plaintext information she wants to send to Bob into ciphertext using a certain encryption rule. Then, it is transmitted to Bob through a public classical channel. Bob uses a decryption key K' to convert the ciphertext back into plaintext using an appropriate decryption rule. If this process can effectively prevent any unauthorized user Eve from eavesdropping, it is considered secure communication.

[0003] Classical communication lacks a verifiable, unconditionally secure secret channel because an eavesdropper can, in principle, always obtain information without leaving a trace. Furthermore, traditional cryptographic techniques rely on mathematical computational complexity to guarantee their security; however, with ever-increasing computing power, especially the development of quantum computers, the security of traditional encryption methods faces significant threats.

[0004] Quantum cryptography is based on the Heisenberg uncertainty principle and the no-cloning theorem for unknown quantum states, guaranteeing its unconditional security through physical principles. The Heisenberg uncertainty principle states that it is impossible to measure the position and momentum of a quantum simultaneously with the same precision, because measuring one physical quantity of a quantum will inevitably change one of its eigenstates and simultaneously disturb the state of another physical quantity. The no-cloning theorem states that it is impossible to replicate a single quantum without knowing its state, because precise replication requires measurement, which inevitably alters the quantum's state.

[0005] Quantum key distribution (QKD) uses the basic principles of quantum physics to ensure communication security. It allows two legitimate users to generate a shared string of secure random bits as a key, and then transmit the key through free space or optical fiber as the transmission channel. Currently, QKD using optical fiber as the transmission channel has made great progress.

[0006] Quantum Keyless Diplomacy (QKD) uses information carried by single photons (light quanta) to negotiate and generate keys between two legitimate users. However, the energy of a single photon is extremely weak and easily affected by other optical signals. Therefore, existing QKD networks mainly use separate fiber optic cables to transmit quantum optical signals, which suffers from long construction periods, high costs, and complex maintenance, hindering the widespread deployment of quantum secure communication services.

[0007] To address this issue, US Patent US7809268B2 describes a method for multiplexing quantum signals and classical signals using the same optical fiber. The principle is as follows: Figure 5 As shown, the main working principle is to multiplex and demultiplex quantum signals with classical signals using wavelength division multiplexing devices.

[0008] However, due to the nonlinear effects of optical fibers, classical signals generate broadband noise during transmission. This noise increases with the intensity of the classical light, affecting the signal-to-noise ratio of the quantum signal and consequently impacting the stable operation of QKD. In practical applications, the intensity of the classical light often varies depending on the network environment. Therefore, when using wavelength division multiplexing (WDM) of classical and quantum signals in different network environments, adjustments to the classical signal are necessary based on the specific circumstances. Existing US patents disclose a method for multiplexing quantum and classical signals using the same optical fiber, but this method cannot adjust the intensity of the classical signal to adapt to different network environments, limiting its applicability. Summary of the Invention

[0009] This invention provides an apparatus and method for transmitting quantum and classical signals via multiplexed optical fiber. By setting up an optical intensity adaptive adjustment device that is communicatively connected to the QKD receiver terminal between the classical signal input module and the first wavelength division multiplexer, the optical intensity adaptive adjustment device automatically adjusts the attenuation coefficient to attenuate the classical signal based on the noise feedback information from the QKD receiver terminal. This achieves adjustment of the classical signal according to the actual network conditions, solving the technical problem that existing methods for transmitting quantum and classical signals via the same optical fiber cannot adjust the optical intensity of the classical signal to adapt to different network environments and have a limited scope of application.

[0010] This invention provides a device for transmitting quantum signals and classical signals via multiplexed optical fiber, comprising: a classical signal input module, a quantum signal and classical signal multiplexing module, an optical fiber link, a quantum signal and classical signal demultiplexing module, a classical signal output module, a QKD transmitter terminal, and a QKD receiver terminal. The quantum signal and classical signal multiplexing module includes an optical intensity adaptive adjustment device and a first wavelength division multiplexer.

[0011] The classical signal input module, the optical intensity adaptive adjustment device, and the first wavelength division multiplexer are connected sequentially via optical fiber.

[0012] The first wavelength division multiplexer is connected to the quantum signal and classical signal demultiplexing module via the optical fiber link;

[0013] The quantum signal and classical signal demultiplexing module and the classical signal output module are connected via optical fiber;

[0014] The first wavelength division multiplexer and the quantum signal and classical signal demultiplexing module are respectively connected to the QKD transmitting terminal and the QKD receiving terminal via optical fibers;

[0015] The light intensity adaptive adjustment device is also communicatively connected to the QKD receiver terminal, and is used to automatically adjust the attenuation coefficient to attenuate the classical signal based on the noise feedback information of the QKD receiver terminal.

[0016] The first wavelength division multiplexer is used to multiplex the attenuated classical signal and the quantum signal.

[0017] Preferably,

[0018] The quantum signal and classical signal multiplexing module also includes an optical intensity monitoring module and a beam splitter connected by optical fiber between the optical intensity adaptive adjustment device and the first wavelength division multiplexer.

[0019] The beam splitter is used to proportionally distribute the attenuated classical signal;

[0020] The light intensity monitoring module is connected to the beam splitter via optical fiber and is used to monitor the attenuated light intensity of the classical signal in real time according to a portion of the classical signal allocated proportionally by the beam splitter.

[0021] Preferably,

[0022] The quantum signal and classical signal demultiplexing module includes a second wavelength division multiplexer;

[0023] The first wavelength division multiplexer is connected to the second wavelength division multiplexer via the optical fiber link;

[0024] The second wavelength division multiplexer is communicatively connected to the QKD receiver terminal and the classical signal output module via optical fibers, and is used to demultiplex the quantum signal and the classical signal from the signal transmitted by multiplexing one optical fiber.

[0025] Preferably,

[0026] The quantum signal and classical signal demultiplexing module also includes a filtering submodule connected by optical fiber between the second wavelength division multiplexer and the QKD receiver terminal.

[0027] Preferably,

[0028] The filtering submodule includes at least one level of filter.

[0029] Preferably,

[0030] When the filtering submodule includes at least two levels of filters, the connection between each level of filters is cascaded.

[0031] Preferably,

[0032] The classical signal input module includes a classical signal generation submodule, a multiplexer, and a first optical amplifier;

[0033] The classical signal generation submodule, the multiplexer, the first optical amplifier, and the optical intensity adaptive adjustment device are connected sequentially via optical fiber.

[0034] Preferably,

[0035] The classic signal output module includes a second optical amplifier, a wavelength division multiplexer, and a classic signal receiving submodule.

[0036] The quantum signal and classical signal demultiplexing module, the second optical amplifier, the wavelength division multiplexer, and the classical signal receiving submodule are connected sequentially via optical fiber.

[0037] This invention provides a method for multiplexing quantum signals and classical signals for optical fiber transmission, comprising:

[0038] The attenuation coefficient is automatically adjusted based on noise feedback information to attenuate the input classical signal.

[0039] The classical and quantum signals, after attenuation adjustment, are multiplexed and transmitted using the same optical fiber link;

[0040] The multiplexed signal of the classical signal and the quantum signal is demultiplexed, and the quantum signal separated by demultiplexing is filtered.

[0041] The output consists of the classical signal separated by demultiplexing and the quantum signal after filtering.

[0042] Preferably,

[0043] After automatically adjusting the attenuation coefficient to attenuate the input classical signal based on noise feedback information, and before multiplexing the attenuated classical signal and quantum signal onto the same optical fiber link for transmission, the process further includes:

[0044] The classical signal, after attenuation adjustment, is allocated proportionally, and the intensity of the attenuated classical signal is monitored in real time based on the portion of the classical signal obtained by proportional allocation.

[0045] As can be seen from the above technical solutions, the embodiments of the present invention have the following advantages:

[0046] 1. This invention provides an apparatus and method for transmitting quantum and classical signals via multiplexed optical fiber. By setting an adaptive optical intensity adjustment device that communicates with the QKD receiver terminal between the classical signal input module and the first wavelength division multiplexer, the adaptive optical intensity adjustment device automatically adjusts the attenuation coefficient to attenuate the classical signal based on the noise feedback information from the QKD receiver terminal. This achieves adjustment of the classical signal according to the actual network conditions, solving the technical problem that existing methods for transmitting quantum and classical signals via the same optical fiber cannot adjust the optical intensity of the classical signal to adapt to different network environments and have a limited scope of application. This increases the convenience and maintainability of network implementation.

[0047] 2. This invention provides an apparatus and method for transmitting quantum signals and classical signals via multiplexed optical fibers. The quantum signals separated by demultiplexing are filtered through multi-stage filters to reduce noise outside the quantum signal wavelength and improve the signal-to-noise ratio of the quantum signal light.

[0048] 3. This invention provides an apparatus and method for transmitting quantum signals and classical signals via multiplexed optical fiber. A beam splitter is placed between an adaptive optical intensity adjustment device and a first wavelength division multiplexer to proportionally allocate the attenuated classical signal. An optical intensity monitoring module connected to the beam splitter monitors the attenuated classical signal intensity in real time based on the proportionally allocated classical signal. This ensures that the attenuated classical signal is not less than a preset amplitude during attenuation adjustment, thus avoiding impact on classical signal communication quality. Furthermore, after attenuation adjustment, the classical signal can be monitored in real time, and an alarm message is reported when an abnormal classical signal amplitude is detected. Attached Figure Description

[0049] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0050] Figure 1 A schematic diagram of one embodiment of a device for multiplexing quantum signals and classical signals for optical fiber transmission provided by an embodiment of the present invention;

[0051] Figure 2 This is a schematic diagram of another embodiment of a device for multiplexing quantum signals and classical signals for optical fiber transmission, provided by an embodiment of the present invention.

[0052] Figure 3 This is a flowchart illustrating a first embodiment of a method for multiplexing quantum signals and classical signals for optical fiber transmission provided by an embodiment of the present invention;

[0053] Figure 4 This is a flowchart illustrating a second embodiment of a method for multiplexing quantum signals and classical signals for optical fiber transmission provided by an embodiment of the present invention;

[0054] Figure 5 This is a schematic diagram of the principle of a method for multiplexing quantum signals and classical signals using the same optical fiber. Detailed Implementation

[0055] This invention provides an apparatus and method for transmitting quantum and classical signals via multiplexed optical fiber. By setting up an optical intensity adaptive adjustment device that is communicatively connected to the QKD receiver terminal between the classical signal input module and the first wavelength division multiplexer, the optical intensity adaptive adjustment device automatically adjusts the attenuation coefficient to attenuate the classical signal based on the noise feedback information from the QKD receiver terminal. This achieves adjustment of the classical signal according to the actual network conditions, solving the technical problem that existing methods for transmitting quantum and classical signals via the same optical fiber cannot adjust the optical intensity of the classical signal to adapt to different network environments and have a limited scope of application.

[0056] To make the objectives, features, and advantages of this invention more apparent and understandable, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described below are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0057] Please see Figure 1This invention provides an embodiment of a device for transmitting quantum and classical signals via multiplexed optical fiber, comprising: a classical signal input module 1, a quantum and classical signal multiplexing module 2, an optical fiber link 4, a quantum and classical signal demultiplexing module 5, a classical signal output module 7, a QKD transmitter terminal 3, and a QKD receiver terminal 6. The classical signal input module 1 is used to input the classical signal to be transmitted; the quantum and classical signal multiplexing module 2 is used to couple classical and quantum signals of different wavelengths into the same optical fiber for multiplexed optical fiber transmission; the optical fiber link 4 is used to transmit optical signals; the quantum and classical signal demultiplexing module 5 is used to separate quantum and classical signals of different wavelengths from the signal transmitted via multiplexed optical fiber; the classical signal output module 7 is used to output the classical signal to be transmitted; QKD refers to a quantum key distribution device used to generate keys; the QKD transmitter terminal 3 can emit quantum optical signals; and the QKD receiver terminal 6 can detect and process the optical signals emitted by the transmitter. It should be noted that both the classical signal input module 1 and the classical signal output module 7 refer to devices used in traditional optical communication networks.

[0058] The quantum signal to classical signal multiplexing module 2 includes an intensity adaptive adjustment device 110, a beam splitter 111, a first wavelength division multiplexer 104, and an intensity monitoring module 112. The classical signal input module 1, the intensity adaptive adjustment device 110, the beam splitter 111, and the first wavelength division multiplexer 104 are sequentially connected via optical fiber. The first wavelength division multiplexer 104 is connected to the quantum signal to classical signal demultiplexing module 5 via optical fiber link 4. The quantum signal to classical signal demultiplexing module 5 is connected to the classical signal output module 7 via optical fiber. The first wavelength division multiplexer 104 and the quantum signal to classical signal demultiplexing module 5 are connected to the QKD transmitting terminal 3 and the QKD receiving terminal 6 via optical fiber, respectively. The intensity adaptive adjustment device 110 also communicates with the QKD receiving terminal 6. The connection is used to automatically adjust the attenuation coefficient based on the noise feedback information of the QKD receiver terminal 6 to attenuate the classical signal input module 1; the beam splitter 111 is used to proportionally distribute the attenuated classical signal; the light intensity monitoring module 112 is connected to the beam splitter 111 via optical fiber, and is used to monitor the light intensity of the attenuated classical signal in real time based on the portion of classical signal distributed by the beam splitter 111, so as to ensure that the classical signal is not less than the preset amplitude after attenuation adjustment, so as not to affect the communication quality of the classical signal. Moreover, after the attenuation adjustment process, the classical signal can also be monitored in real time, and when an abnormal classical signal amplitude is detected, an alarm message will be reported; the first wave division multiplexer 104 is used to multiplex the attenuated classical signal and the quantum signal.

[0059] It should be noted that in the quantum signal and classical signal multiplexing module 2, the optical intensity adaptive adjustment device 110 and the first wavelength division multiplexer 104 are necessary technical features to solve the technical problem that existing methods for multiplexing quantum signals and classical signals on the same optical fiber cannot adjust the optical intensity of the classical signal to adapt to different network environments and have a limited scope of application. The remaining technical features in the quantum signal and classical signal multiplexing module 2 are further optimizations of the device for multiplexing quantum signals and classical signals on optical fiber provided in this embodiment. It can be understood that the optical intensity adaptive adjustment device 110, the first wavelength division multiplexer 104, the classical signal input module 1, the optical fiber link 4, the quantum signal and classical signal demultiplexing module 5, the classical signal output module 7, the QKD transmitter terminal 3, and the QKD receiver terminal 6 can cooperate with each other to adjust the classical signal according to the actual network conditions.

[0060] The quantum signal and classical signal demultiplexing module 5 includes a second wavelength division multiplexer 105 and a filtering submodule 106. The first wavelength division multiplexer 104 is connected to the second wavelength division multiplexer 105 via an optical fiber link 4. The second wavelength division multiplexer 105 is connected to the QKD receiver terminal 6 and the classical signal output module 7 via optical fibers. The filtering submodule 106 is connected between the second wavelength division multiplexer 105 and the QKD receiver terminal 6 via an optical fiber. The filtering submodule 106 includes at least one stage of filtering; when the filtering submodule 106 includes at least two stages of filtering... The filters are connected in a cascaded manner. The filter submodule 106 is used to filter the quantum signal, remove noise in other bands besides the quantum signal wavelength, and improve the signal-to-noise ratio of the quantum signal light. The number of cascaded filters is within a certain range. The filtering effect of the filter submodule 106 increases with the increase of the number of filters cascaded. The number of filters cascaded in the filter submodule 106 can be configured according to the actual network situation. The second wavelength division multiplexer 105 is used to demultiplex the quantum signal and the classical signal from the signal transmitted by multiplexing one optical fiber.

[0061] It should be noted that in the quantum signal and classical signal demultiplexing module 5, the second wavelength division multiplexer 105 is a necessary technical feature to solve the technical problem that the existing method of multiplexing quantum signals and classical signals for transmission on the same optical fiber cannot adjust the light intensity of the classical signal to adapt to different network environments and has a small scope of application. The filtering submodule 106 only filters the demultiplexed quantum signal and is a further optimization of the device for multiplexing quantum signals and classical signals for transmission on optical fiber provided in this embodiment.

[0062] The classic signal input module 1 includes a classic signal generation submodule 100, a multiplexer 101, and a first optical amplifier 102;

[0063] The classical signal generation submodule 100, the multiplexer 101, the first optical amplifier 102, and the optical intensity adaptive adjustment device 110 are connected in sequence via optical fiber. The classical signal generation submodule 100 is used to generate classical signals, the multiplexer 101 is used to combine multiple classical signals with different wavelengths, and the first optical amplifier 102 is used to amplify the combined classical signal.

[0064] The classic signal output module 7 includes a second optical amplifier 107, a demultiplexer 108, and a classic signal receiving submodule 109;

[0065] The quantum signal and classical signal demultiplexing module 5, the second optical amplifier 107, the wavelength divider 108, and the classical signal receiving submodule 109 are connected in sequence via optical fiber. The second optical amplifier 107 is used to amplify the classical signal separated by demultiplexing. The wavelength divider 108 is used to separate the classical signal amplified by the second optical amplifier 107 into multiple single classical signals. The classical signal receiving submodule 109 is used to receive multiple single classical signals.

[0066] The above is a detailed description of the structure and connection method of a device for multiplexing quantum signals and classical signals using optical fiber. For ease of understanding, the following will illustrate the application of this device in a specific scenario, including:

[0067] Please see Figure 2 When the classical signal output from the classical signal input module 1 passes through the quantum signal and classical signal multiplexing module 2, it successively passes through the optical intensity adaptive adjustment device 110, the beam splitter 111, and the optical intensity monitoring module 112. The optical intensity adaptive adjustment device 110 automatically adjusts its attenuation value based on the noise information fed back by the QKD receiver terminal 6 through the classical network. After attenuation, the classical signal passes through the beam splitter 111 with a splitting ratio of 1:999. The classical signal with an intensity of 1‰ of the classical signal enters the optical intensity monitoring module 112. The optical intensity monitoring module 112 calculates the intensity of the attenuated classical signal based on the detected signal intensity, ensuring that the attenuated classical signal is not less than a preset threshold (the preset threshold is the minimum classical signal intensity allowed under the premise of ensuring classical communication quality in classical communication). When the noise generated by the classic signal after attenuation adjustment by the light intensity adaptive adjustment device 110 does not affect the stable operation of the QKD device, and the light intensity of the classic signal is not less than the preset threshold of the monitoring module, the classic signal light intensity adaptive adjustment operation is completed. At this time, the attenuation setting of the light intensity adaptive adjustment device 110 is locked, and the device records the attenuated classic signal light intensity as the reference light intensity. When the device detects a large deviation between the classic signal light intensity and the reference light intensity during operation (the threshold is set to 5%), it will automatically report an alarm message.

[0068] In this embodiment of the invention, a 1310nm quantum signal and a 1550nm classical signal are used. The first wavelength division multiplexer 104 has a specification of 1550 / 1310. Its Pass interface is connected to the optical splitter 111, its Reflection interface is connected to the QKD transmitter terminal 3, and its Com interface is connected to the optical fiber link 4. The Pass to Com optical path can carry the 1550nm classical signal, and the Reflection to Com optical path can carry the 1310nm quantum signal. The first wavelength division multiplexer 104 realizes the mixing of the 1310nm quantum signal and the classical signal. The 1550nm classical signal is bundled; the second wavelength division multiplexer 105 has a specification of 1310 / 1550, its Com interface is connected to fiber optic link 4, its Pass interface is connected to filter submodule 106, and its Reflection interface is connected to the second optical amplifier 107. The Com to Pass optical path can separate the 1310nm quantum signal, and the Com to Reflection optical path can separate the 1550nm classical signal. The second wavelength division multiplexer 105 separates the 1310nm quantum signal and the 1550nm classical signal from the multiplexed signal.

[0069] Table 1 compares the detection noise of QKD receiver terminal 6 before and after adaptive adjustment of the classical signal intensity. It can be seen that, under the premise of ensuring the quality of classical communication, attenuating the classical signal can effectively reduce the noise detected by QKD receiver terminal 6. At the same time, the code generation rate of QKD receiver terminal 6 is significantly improved, indicating that the detection noise is reduced after adaptive adjustment of the classical signal intensity, which is beneficial to the stable operation of QKD receiver terminal 6.

[0070] Table 1

[0071]

[0072] Classical and quantum signals are multiplexed into the same optical fiber link 4 via the first wavelength division multiplexer 104 for transmission;

[0073] When the signal reaches the quantum signal and classical signal demultiplexing module 5, it first passes through the second wavelength division multiplexer 105 to separate the classical signal and the quantum signal. The separated classical signal is transmitted to the classical signal output module 7 and received and processed. The separated quantum signal is filtered by the filtering submodule 106 with a center wavelength of 1310nm, and then transmitted to the QKD receiver terminal 6 for detection and processing.

[0074] Figure 2The intermediate filtering submodule 106 uses two filters cascaded together with a center wavelength of 1310nm. The multi-stage filter can increase the isolation of the quantum signal wavelength channel from noise of other wavelengths and further filter out noise. To compare the effects, under the same classical signal multiplexing conditions, a single-stage filter and a two-stage filter are compared respectively. The results are shown in Table 2. It can be seen that using a two-stage filter can effectively reduce noise and improve the code generation rate of the QKD receiver terminal 6, thus proving that using at least one stage filter to filter the quantum signal at the demultiplexing end can improve the signal-to-noise ratio of the quantum signal.

[0075] Table 2

[0076]

[0077] Please see Figure 3 The present invention provides a first embodiment of a method for multiplexing quantum signals and classical signals for optical fiber transmission, comprising:

[0078] 131. The attenuation coefficient is automatically adjusted based on noise feedback information to attenuate the input classical signal.

[0079] In this embodiment of the invention, the attenuation coefficient is first automatically adjusted based on the noise feedback information to attenuate the input classical signal.

[0080] 132, attenuated classical and quantum signals are multiplexed and transmitted using the same optical fiber link;

[0081] In this embodiment of the invention, after automatically adjusting the attenuation coefficient to attenuate the input classical signal based on noise feedback information, it is also necessary to multiplex the attenuated classical signal and the quantum signal using the same optical fiber link for transmission.

[0082] 133, Demultiplexing the multiplexed signals of classical and quantum signals and filtering the quantum signals separated by demultiplexing;

[0083] In this embodiment of the invention, after transmitting the attenuated classical signal and quantum signal through the same optical fiber link, it is necessary to demultiplex the multiplexed signal and the quantum signal separated by demultiplexing and then filter the quantum signal.

[0084] 134, outputs the classical signal separated by demultiplexing and the filtered quantum signal;

[0085] In this embodiment of the invention, after demultiplexing the multiplexed classical signal and quantum signal and filtering the quantum signal separated by demultiplexing, it is also necessary to output the classical signal separated by demultiplexing and the filtered quantum signal.

[0086] Please see Figure 4 This invention provides a second embodiment of a method for multiplexing quantum signals and classical signals for optical fiber transmission, comprising:

[0087] 121. The attenuation coefficient is automatically adjusted based on noise feedback information to adjust the attenuation of the input classical signal;

[0088] In this embodiment of the invention, the attenuation coefficient is first automatically adjusted based on the noise feedback information to attenuate the input classical signal.

[0089] 122. Distribute the attenuated classical signal proportionally and monitor the intensity of the attenuated classical signal in real time based on the proportionally distributed portion of the classical signal.

[0090] In this embodiment of the invention, after automatically adjusting the attenuation coefficient to attenuate the input classical signal based on noise feedback information, it is also necessary to proportionally allocate the attenuated classical signal and monitor the intensity of the attenuated classical signal in real time based on the proportionally allocated portion of the classical signal. When the noise generated by the attenuated classical signal does not affect the stable operation of the QKD device, and the intensity of the classical signal is not less than a preset threshold, the adaptive adjustment operation of the classical signal intensity is completed. At this time, the attenuation setting is locked, and the device records the locked classical signal intensity after attenuation as the reference intensity. When the device detects a large deviation between the monitored classical signal intensity and the reference intensity (e.g., the threshold is set to 5%) during operation, it will automatically report an alarm message.

[0091] 123, multiplexing classical and quantum signals, after attenuation adjustment, into the same optical fiber link for transmission;

[0092] In this embodiment of the invention, after proportionally allocating the attenuated classical signal and monitoring the intensity of the attenuated classical signal in real time based on the proportionally allocated portion of the classical signal, it is also necessary to multiplex the attenuated classical signal and the quantum signal using the same optical fiber link for transmission. It should be noted that the attenuated classical signal mentioned here is actually a portion of the classical signal obtained after proportionally allocating the attenuated classical signal.

[0093] 124. Demultiplex the multiplexed classical and quantum signals and filter the quantum signals separated by demultiplexing;

[0094] In this embodiment of the invention, after transmitting the attenuated classical signal and quantum signal through the same optical fiber link, it is necessary to demultiplex the multiplexed signal and the quantum signal separated by demultiplexing and then filter the quantum signal.

[0095] 125, outputs the classical signal separated by demultiplexing and the filtered quantum signal;

[0096] In this embodiment of the invention, after demultiplexing the multiplexed classical signal and quantum signal and filtering the quantum signal separated by demultiplexing, it is also necessary to output the classical signal separated by demultiplexing and the filtered quantum signal.

[0097] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working processes of the systems, devices, and units described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here.

[0098] In the several embodiments provided in this application, it should be understood that the disclosed systems, apparatuses, and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces, or indirect coupling or communication connection between apparatuses or units, and may be electrical, mechanical, or other forms.

[0099] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0100] Furthermore, the functional units in the various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0101] If the integrated unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art, or all or part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of the present invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0102] As described above, the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that the technical solutions described in the above embodiments can still be modified, or some of the technical features thereof can be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A device for multiplexing quantum signals and classical signals for optical fiber transmission, comprising: The classical signal input module, the quantum signal and classical signal multiplexing module, the optical fiber link, the quantum signal and classical signal demultiplexing module, the classical signal output module, the QKD transmitter terminal, and the QKD receiver terminal are characterized in that the quantum signal and classical signal multiplexing module includes an optical intensity adaptive adjustment device and a first wavelength division multiplexer. The classical signal input module, the optical intensity adaptive adjustment device, and the first wavelength division multiplexer are connected sequentially via optical fiber. The first wavelength division multiplexer is connected to the quantum signal and classical signal demultiplexing module via the optical fiber link; The quantum signal and classical signal demultiplexing module and the classical signal output module are connected via optical fiber; The first wavelength division multiplexer and the quantum signal and classical signal demultiplexing module are connected to the QKD transmitting terminal and the QKD receiving terminal respectively via optical fibers; the QKD transmitting terminal is used to emit quantum signals, and the QKD receiving terminal is used to detect and process the quantum signals emitted by the QKD transmitting terminal to obtain noise feedback information; The light intensity adaptive adjustment device is also communicatively connected to the QKD receiver terminal, and is used to automatically adjust the attenuation coefficient to attenuate the classical signal based on the noise feedback information of the QKD receiver terminal. The first wavelength division multiplexer is used to multiplex the attenuated classical signal and the quantum signal; The quantum signal and classical signal multiplexing module further includes an optical intensity monitoring module and a beam splitter connected by optical fiber between the optical intensity adaptive adjustment device and the first wavelength division multiplexer. The beam splitter is used to proportionally distribute the attenuated classical signal; The light intensity monitoring module is connected to the beam splitter via optical fiber and is used to monitor the attenuated light intensity of the classical signal in real time according to a portion of the classical signal allocated proportionally by the beam splitter.

2. The device for multiplexing quantum signals and classical signals for optical fiber transmission according to claim 1, characterized in that, The quantum signal and classical signal demultiplexing module includes a second wavelength division multiplexer; The first wavelength division multiplexer is connected to the second wavelength division multiplexer via the optical fiber link; The second wavelength division multiplexer is communicatively connected to the QKD receiver terminal and the classical signal output module via optical fibers, and is used to demultiplex the quantum signal and the classical signal from the signal transmitted by multiplexing one optical fiber.

3. The device for multiplexing quantum signals and classical signals for optical fiber transmission according to claim 2, characterized in that, The quantum signal and classical signal demultiplexing module also includes a filtering submodule connected by optical fiber between the second wavelength division multiplexer and the QKD receiver terminal.

4. The device for multiplexing quantum signals and classical signals for optical fiber transmission according to claim 3, characterized in that, The filtering submodule includes at least one level of filter.

5. The device for multiplexing quantum signals and classical signals for optical fiber transmission according to claim 4, characterized in that, When the filtering submodule includes at least two levels of filters, the connection between each level of filters is cascaded.

6. The apparatus for multiplexing quantum signals and classical signals for optical fiber transmission according to any one of claims 1 to 5, characterized in that, The classical signal input module includes a classical signal generation submodule, a multiplexer, and a first optical amplifier; The classical signal generation submodule, the multiplexer, the first optical amplifier, and the optical intensity adaptive adjustment device are connected sequentially via optical fiber.

7. The apparatus for multiplexing quantum signals and classical signals for optical fiber transmission according to any one of claims 1 to 5, characterized in that, The classic signal output module includes a second optical amplifier, a wavelength division multiplexer, and a classic signal receiving submodule. The quantum signal and classical signal demultiplexing module, the second optical amplifier, the wavelength division multiplexer, and the classical signal receiving submodule are connected sequentially via optical fiber.

8. A method for multiplexing quantum signals and classical signals for optical fiber transmission, characterized in that, The method is based on the apparatus for multiplexing quantum signals and classical signals in optical fiber as described in any one of claims 1-7, comprising: The attenuation coefficient is automatically adjusted based on noise feedback information to attenuate the input classical signal. The classical and quantum signals, after attenuation adjustment, are multiplexed and transmitted using the same optical fiber link; The multiplexed signal of the classical signal and the quantum signal is demultiplexed, and the quantum signal separated by demultiplexing is filtered. The output consists of the classical signal separated by demultiplexing and the quantum signal after filtering. The process includes, after automatically adjusting the attenuation coefficient to attenuate the input classical signal based on noise feedback information, and before multiplexing the attenuated classical signal and quantum signal onto the same optical fiber link for transmission, the following steps are also included: The classical signal, after attenuation adjustment, is allocated proportionally, and the intensity of the attenuated classical signal is monitored in real time based on the portion of the classical signal obtained by proportional allocation.

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