A downlink CV-QKD access network method and system based on wavelength division multiplexing

Abstract

The present invention provides a downlink CV-QKD access network method and system based on wavelength division multiplexing, including: step 1, generating a multi-wavelength multiplexing light source at the central node; step 2, modulating the key information to be sent onto the multi-wavelength multiplexing light source; step 3, adjusting the light intensity of the quantum signal of the central node through the optical attenuation module and sending the adjusted quantum light signal to the transmission link; step 4, the user end receives the quantum signal through the transmission link, demultiplexes the quantum light signals of different wavelengths through the wavelength division multiplexer, and sends them to different users; step 5, each user performs quantum measurement internally, and completes quantum key distribution after data processing. The present invention reduces the cost of the central node and simplifies the network structure. Compared with a one-to-many CV-QKD system using a splitter or other similar structures, the present invention will not reduce the transmission performance as the number of users increases.

Description

Technical Field

[0001] The present invention relates to the field of quantum key distribution, and in particular to a downlink CV-QKD access network method and system based on wavelength division multiplexing. Background Art

[0002] Quantum secure communication has become an important technical direction for dealing with information security threats due to its information-theoretic security characteristics. Among them, quantum key distribution (QKD) is one of the most important technical approaches to achieve quantum secure communication. In recent years, typical point-to-point QKD links have made great progress in protocols, components, and system integration, and have begun to be promoted for commercial applications. From the perspective of the overall QKD network, point-to-point QKD links are suitable for forming a backbone quantum core network for long-distance quantum secure communications. For example, in 2021, a research team from the University of Science and Technology of China realized a QKD wide-area network spanning 4,600 kilometers through satellite-to-ground links. However, in the multi-user access network of the "last mile", point-to-point QKD is not very applicable due to system cost considerations. Therefore, it is of great application value to build a point-to-multipoint low-cost QKD access network for multiple users. From the perspective of QKD access network architecture, in 2005, PD Kumavor et al. from the University of Connecticut in the United States roughly divided QKD access networks into four types, including: (1) star-shaped passive QKD network based on 1-way beam splitter; (2) ring-shaped multi-user QKD network based on Sagnac interferometer; (3) star-shaped passive QKD network based on wavelength division multiplexing; (4) QKD network based on wavelength addressable bus. Among them, the first and third solutions are the most typical, and these two solutions are more compatible with the existing passive optical access network. Therefore, the research status of these two solutions will be elaborated in detail below.

[0003] As early as 1997, British Telecom PD Townsend experimentally verified the QKD access network on a 1-to-3 passive optical network, where the central node sends key information to users in the downlink, and users detect the quantum light signals separately. This structure has two defects. First, each user needs a single-photon detector to measure the quantum state, which increases the cost of the user end. Second, all single-photon detectors must run at the speed of quantum state preparation at the transmitting end to avoid missing photons, which means that most of the detector bandwidth is not used. Based on this, B. et al. proposed an uplink QKD link in 2013, that is, the user generates a quantum key optical signal and transmits it to the central node (such as an optical link terminal, etc.) through a passive transmission link after combining it through a beam combiner, and the quantum optical signals of different users are detected at the central node in a time-sharing manner. At this time, only a single-photon detector is needed at the central node to detect the quantum signal, which greatly reduces the user-side cost. They also experimentally verified that 64 quantum optical signals were received by a single-photon detector, and analyzed the coding rate of the link in detail. The above two schemes are based on the research of discrete variable (Discrete Variable, DV) QKD system, and their cost is still very high for large-scale user access application scenarios. Therefore, the continuous variable (Continuous Variable, CV) QKD technology, which is more compatible with existing optical fiber networks, has become an important candidate for QKD access network.

[0004] CV-QKD technology can use commercial optical components for quantum signal generation, transmission, detection and processing, etc. At the same time, it is much less affected by traditional optical communication signals than DV-QKD. Therefore, for QKD access networks, CV-QKD has a more prominent advantage. From 2019 to 2020, Beijing University of Posts and Telecommunications applied for a number of patents related to CV-QKD access networks, including an uplink continuous variable quantum key distribution access network method using a wavelength division multiplexer, an uplink continuous variable quantum key distribution access network method using an optical splitter, a quantum access network architecture and method based on multi-core optical fiber, and an uplink continuous variable quantum key distribution access network method. In 2021, Q. Liao and others from Central South University proposed a multi-user structure based on CV-QKD and conducted a theoretical analysis. In the same year, D. from the Austrian Institute of Technology et al. proposed a scheme for co-fiber transmission based on wavelength division multiplexing and 5G multi-user CV-QKD network integration.

[0005] Obviously, the downlink QKD access network method based on beam splitters has the simplest structure, which is also the solution adopted by mainstream commercial passive optical networks at this stage. However, as the number of users N increases, the link attenuation increases by 10×log10(N)dB. For QKD systems that are particularly sensitive to link attenuation, this solution can only support a limited number of users in the QKD access network. Although the uplink QKD access network based on beam splitters will not directly affect the QKD performance as the number of users increases, the user end needs to independently complete the quantum state preparation, which not only increases the user end cost, but also requires high synchronization of the quantum state preparation and transmission time of each user when the central node measures the quantum state. The star-shaped passive QKD network based on wavelength division multiplexing is a solution in which the link attenuation is independent of the number of access users. However, this solution either uses quantum optical signals of different wavelengths to match different users in different time intervals, or uses multiple sets of quantum optical signal generating devices of different wavelengths. Therefore, the current QKD access network method based on wavelength division multiplexing cannot achieve simultaneous coding of multiple users and effectively control the system cost. In summary, the present invention proposes a downlink continuous variable quantum key distribution access network method based on wavelength division multiplexing, which adopts a wavelength division multiplexing scheme, and realizes the generation of multi-wavelength quantum signals by multiplexing multi-wavelength optical signals at the central node after electro-optical modulation and optical attenuation. This reduces the complexity and cost of the QKD access network, and also ensures the simultaneous coding of different users. Summary of the invention

[0006] In view of the problems existing in the prior art, a downlink CV-QKD access network method and system based on wavelength division multiplexing are provided, which solves the one-to-many architecture design optimization problem in the multi-user CV-QKD access network, and constructs a more practical multi-user CV-QKD access network structure from the two perspectives of multi-user simultaneous coding and system complexity.

[0007] The technical solution adopted by the present invention is as follows: A downlink CV-QKD access network method based on wavelength division multiplexing, comprising the following steps:

[0008] Step 1: Generate a multi-wavelength multiplexing light source at the central node;

[0009] Step 2, modulating the key information to be sent onto a multi-wavelength multiplexing light source;

[0010] Step 3: Adjust the light intensity of the quantum signal of the central node through the optical attenuation module and send the adjusted quantum light signal to the transmission link;

[0011] Step 4: The user end receives the quantum signal through the transmission link, demultiplexes the quantum optical signals of different wavelengths through the wavelength division multiplexer, and sends them to different users;

[0012] Step 5: Each user performs quantum measurement internally, and after data processing, quantum key distribution is completed.

[0013] Furthermore, in step 1, the multi-wavelength multiplexed light source is generated by multiple independent lasers, optical frequency combs or hybrid multiplexing.

[0014] Furthermore, in step 2, an electro-optical modulation module is used to simultaneously modulate multiple independent key signals carrying key information onto different wavelengths.

[0015] Furthermore, in step 3, an optical attenuator is used to uniformly attenuate optical signals of all wavelengths, or an optical waveform shaper is used to control the attenuation of optical signals of different wavelengths.

[0016] Furthermore, in step 5, quantum measurement is performed using homodyne or heterodyne coherent detection, and the local oscillator light source for coherent detection is generated by a central node and transmitted to the user end along with the quantum light signal, or is generated at the user end using an independent laser source.

[0017] Furthermore, the data processing includes phase compensation, polarization compensation, other link damage compensation, basis vector comparison, parameter estimation, data negotiation, error correction and private key amplification of the detected quantum signal.

[0018] The present invention also proposes a downlink CV-QKD access network system based on wavelength division multiplexing, including a central node and a user end, wherein the central node is connected to the user end via a transmission link;

[0019] The central node includes M light source modules, a wavelength division multiplexing module, a continuous variable quantum light and reference signal generation module, and an electrical signal generation module. The M light source modules can generate at least N optical carriers with different wavelengths, and synthesize them into a beam of multi-wavelength carriers through the wavelength division multiplexing module; the electrical signal generation module generates an electrical signal containing original key information, and the electrical signal and the multi-wavelength carrier are modulated in the continuous variable quantum light and reference signal generation module to generate the required modulated quantum light signal and reference signal, and send them to the transmission link;

[0020] The user end includes a wavelength division multiplexing module and N users. The received modulated quantum light signal is demultiplexed through the wavelength division multiplexing module and distributed to N users. Each user uses coherent detection to measure the quantum signal and performs digital signal processing on the detected quantum signal through a reference signal to complete quantum key distribution.

[0021] Furthermore, the electrical signal generating module includes a random signal generating module, an encoding module, a digital-to-analog conversion module and a driving amplification module which are connected in sequence.

[0022] Furthermore, the continuous variable quantum light and reference signal generating module includes a beam splitter, an electro-optical modulation module, a delay control module, a first optical attenuation module, a second optical attenuation module, a first polarization control module, a second polarization control module and a polarization combiner; the multi-wavelength carrier output by the wavelength division multiplexing module is divided into two paths by the beam splitter, one of which is processed by the electro-optical modulation module, the first optical attenuation module, and the first polarization control module in sequence and enters the polarization combiner, and the other is processed by the delay control module, the second optical attenuation module, and the second polarization control module in sequence and enters the polarization combiner, which is combined by the polarization combiner and then output; wherein the electro-optical modulation module also simultaneously receives the electrical signal of the original key information generated by the electrical signal generating module, and modulates the electrical signal onto the multi-wavelength carrier.

[0023] Furthermore, when the user measures quantum signals, he or she adopts homodyne or heterodyne coherent detection to measure. The local oscillator light source of the coherent detection is generated by the central node and transmitted to the user end along with the quantum light signal, or, it is generated by an independent laser source at the user end.

[0024] Compared with the prior art, the beneficial effects of adopting the above technical solution are: the present invention reduces the cost of the central node and simplifies the network structure. Compared with the one-to-many CV-QKD system using a splitter or other similar structures, the present invention will not reduce the transmission performance as the number of users increases. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a flow chart of the downlink CV-QKD access network method based on wavelength division multiplexing proposed by the present invention.

[0026] Figure 2 This is a structural diagram of the downlink CV-QKD access network system based on wavelength division multiplexing proposed by the present invention.

[0027] Figure 3 This is a structural diagram of a continuous variable quantum light and reference light signal generating module in one embodiment of the present invention. DETAILED DESCRIPTION

[0028] Embodiments of the present application are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar modules or modules with the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present application, and cannot be construed as limitations on the present application. On the contrary, the embodiments of the present application include all changes, modifications and equivalents that fall within the spirit and connotation of the appended claims.

[0029] Example 1

[0030] This embodiment adopts wavelength division multiplexing. At the central node, the multi-wavelength multiplexing light source is used to load the original key signal to be sent onto the wavelength division multiplexing light source carrier through an electro-optical modulation module, and is transmitted to different users at the user end through wavelength division multiplexing, thereby constructing a downlink continuous variable quantum key distribution access network based on wavelength division multiplexing. The specific scheme is as follows:

[0031] like Figure 1 As shown, a downlink CV-QKD access network method based on wavelength division multiplexing includes the following steps:

[0032] Step 1: Generate a multi-wavelength multiplexing light source at the central node;

[0033] Step 2, modulating the key information to be sent onto a multi-wavelength multiplexing light source;

[0034] Step 3: Adjust the light intensity of the quantum signal of the central node through the optical attenuation module and send the adjusted quantum light signal to the transmission link;

[0035] Step 4: The user end receives the quantum signal through the transmission link, demultiplexes the quantum optical signals of different wavelengths through the wavelength division multiplexer, and sends them to different users;

[0036] Step 5: Each user performs quantum measurement internally, and after data processing, quantum key distribution is completed.

[0037] In this embodiment, the transmission link can be implemented by using a passive optical fiber network, a free space network, or the like.

[0038] Specifically, in step 1, the multi-wavelength multiplexing light source serves as a carrier of the subsequent modulated signal, and can be generated by multiple independent lasers, optical frequency combs, or hybrid multiplexing.

[0039] In step 2, the key information is generated by the electrical signal generation module, and then the electro-optical modulation module is used to simultaneously modulate multiple independent key signals carrying the key information onto different wavelengths. Compared with the wavelength division multiplexing transmission scheme, this method can reduce the number of electro-optical modulation modules and electrical signal generation modules required by the central node, simplify the internal structure of the access network central station and reduce system costs. At the same time, compared with the downlink QKD access network method based on the beam splitter, this method will not directly affect the QKD performance as the number of users increases.

[0040] In this embodiment, the electro-optical modulation module may be an intensity modulator, a phase modulator, an IQ modulator, etc., which is mainly determined by the protocol adopted by the QKD system.

[0041] The optical signal emitted by the electro-optical modulation module is a high-power light, so the strong light signal needs to be attenuated to the quantum light intensity range. In step 3, an optical attenuator is used to achieve uniform attenuation of all wavelength optical signals, or an optical waveform shaper is used to control the attenuation of optical signals of different wavelengths, so that each wavelength quantum optical signal has an optimal modulation variance output.

[0042] In step 5, quantum measurement includes coherent detection methods such as homodyne or heterodyne. The local oscillator light source of coherent detection can be generated by a central node and transmitted to the user end with the quantum light signal (path-based local oscillator), or it can be generated by an independent laser source at the user end (local local oscillator). The data processing includes phase compensation, polarization compensation, other link damage compensation, basis vector comparison, parameter estimation, data negotiation, error correction, and private key amplification of the detected quantum signal. Among them, parameter estimation includes calculating key parameters such as signal-to-noise ratio and security code rate of the compensated signal.

[0043] Example 2

[0044] The present invention also proposes a downlink CV-QKD access network system based on wavelength division multiplexing, such as Figure 2 As shown, it includes a central node and a user end, and the central node is connected to the user end through a transmission link;

[0045] The central node includes M light source modules, a wavelength division multiplexing module, a continuous variable quantum light and reference signal generation module, and an electrical signal generation module. The M light source modules can generate at least N optical carriers with different wavelengths, and synthesize them into a beam of multi-wavelength carriers through the wavelength division multiplexing module; the electrical signal generation module generates an electrical signal containing original key information, and the electrical signal and the multi-wavelength carrier are modulated in the continuous variable quantum light and reference signal generation module to generate the required modulated quantum light signal and reference signal, and send them to the transmission link; wherein, M is greater than N;

[0046] The user end includes a wavelength division multiplexing module and N users. The received modulated quantum light signal is demultiplexed through the wavelength division multiplexing module and distributed to N users. Each user uses coherent detection to measure the quantum signal and performs digital signal processing on the detected quantum signal through a reference signal to complete quantum key distribution.

[0047] In this embodiment, the transmission link is implemented by using a passive optical fiber network, a free space network, or the like.

[0048] It should be noted that in the central node, when the light source module is generated by a multi-wavelength optical signal generating device such as an optical frequency comb and can meet the needs of the user end, a wavelength division multiplexing module is not required.

[0049] In this embodiment, the electrical signal generating module includes a random signal generating module, an encoding module, a digital-to-analog conversion module and a driving amplification module which are connected in sequence, and is used to generate the required electrical signal containing key information.

[0050] Furthermore, after the user end demultiplexes the quantum optical signal through the wavelength division multiplexing module, it can be transmitted to each user through their respective transmission links.

[0051] In this embodiment, each user uses homodyne or heterodyne coherent detection to measure quantum signals. The local oscillator light source for coherent detection can be generated by a central node and transmitted to the user end along with the quantum light signal (on-path local oscillator), or it can be generated at the user end using an independent laser source (local local oscillator).

[0052] Each user can perform digital signal processing on the detected quantum signal through a strong reference signal or other similar forms, and compensate for effects including frequency deviation, phase noise, and polarization disturbance. After the digital signal processing involved above is completed, the key parameters of the system such as modulation variance, link loss, link over-noise, etc. are obtained through parameter estimation, and the system signal-to-noise ratio and security code rate are calculated based on this, providing a reference for the subsequent data post-processing process. Among them, data post-processing mainly includes data negotiation, error correction, private key amplification and other processes, and finally realizes quantum key distribution.

[0053] like Figure 3 The figure shows a schematic diagram of the continuous variable quantum light and reference signal generation module proposed in this embodiment, which includes a beam splitter, an electro-optical modulation module, a delay control module, a first optical attenuation module, a second optical attenuation module, a first polarization control module, a second polarization control module and a polarization beam combiner;

[0054] The multi-wavelength carrier output by the wavelength division multiplexing module is divided into two paths by the beam splitter, one of which is processed by the electro-optical modulation module, the first optical attenuation module, and the first polarization control module in turn, and enters the polarization beam combiner. The multi-wavelength light source signal is injected into the electro-optical modulation module and multiple independent original key electrical signals are simultaneously loaded onto optical carriers of different wavelengths. Compared with the wavelength division multiplexing transmission scheme, the generation of wavelength division multiplexing quantum optical signals by this method can reduce the number of electro-optical modulation modules and electrical signal generation modules required by the central node, simplify the internal structure of the access network central station and reduce the system cost. Then, the modulated output strong light signal is attenuated to the quantum light intensity range by the first optical attenuation module, and then the first polarization control module aligns the polarization direction of the quantum light signal with the main axis of the polarization beam combiner, and inputs the quantum light signal to an interface of the polarization beam combiner. Among them, the optical attenuation module can be an optical attenuator with fixed attenuation, or an optical waveform shaper to realize the control of the attenuation amount of different wavelengths, and the independent original key electrical signal in the electro-optical modulation module is generated by the electrical signal generation module.

[0055] The other path of the beam splitter is processed by the delay control module, the second optical attenuation module, and the second polarization control module in sequence. The multi-wavelength light source signal is used as the reference light and passes through the delay control module, the second optical attenuation module, and the second polarization control module to control the time delay, light intensity, polarization state and other information of the reference light relative to the quantum light. Finally, the quantum light signal and the reference signal are synthesized into an optical signal through the polarization combiner for output.

[0056] It should be noted that the continuous variable quantum light and reference signal generation module proposed in this embodiment is only a method for realizing continuous variable quantum light and reference light signals based on polarization multiplexing. In addition, the optical signal generation required by the present invention can also be realized through time division multiplexing, frequency division multiplexing and corresponding hybrid multiplexing methods.

[0057] Compared with point-to-point or other wavelength division multiplexing CV-QKD system architectures, the wavelength division multiplexing-based downlink CV-QKD access network system proposed by the present invention reduces the cost of the central node and simplifies the network structure. Compared with a one-to-many CV-QKD system using a splitter or other similar structures, the present invention does not reduce the transmission performance as the number of users increases.

[0058] It should be noted that in the description of the embodiments of the present invention, unless otherwise clearly specified and limited, the terms "setting" and "connection" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a direct connection, or an indirect connection through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances; the drawings in the embodiments are used to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. The components of the embodiments of the present invention generally described and shown in the drawings herein can be arranged and designed in various different configurations.

[0059] Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limitations on the present application. Ordinary technicians in this field can change, modify, replace and modify the above embodiments within the scope of the present application.

Claims

1. A downlink CV-QKD access network method based on wavelength division multiplexing, It is characterized in that The following steps are involved: Step 1: Generate a multi-wavelength multiplexing light source at the central node; Step 2, modulating the key information to be sent onto a multi-wavelength multiplexing light source; Step 3: Adjust the quantum signal light intensity of the central node through the optical attenuation module and send the adjusted quantum light signal to the transmission link; Step 4: The user end receives the quantum signal through the transmission link, demultiplexes the quantum optical signals of different wavelengths through the wavelength division multiplexer, and sends them to different users; Step 5: Each user performs quantum measurement internally, and after data processing, completes quantum key distribution; In the step 2, an electro-optical modulation module is used to simultaneously modulate multiple independent key signals carrying key information onto different wavelengths.

2. The downlink CV-QKD access network method based on wavelength division multiplexing according to claim 1, It is characterized in that In step 1, the multi-wavelength multiplexed light source is generated by multiple independent lasers, optical frequency combs or hybrid multiplexing.

3. The downlink CV-QKD access network method based on wavelength division multiplexing according to claim 1, It is characterized in that In step 3, an optical attenuator is used to uniformly attenuate optical signals of all wavelengths, or an optical waveform shaper is used to control the attenuation of optical signals of different wavelengths.

4. The downlink CV-QKD access network method based on wavelength division multiplexing according to claim 1, It is characterized in that In step 5, quantum measurement is performed using homodyne or heterodyne coherent detection, and the local oscillator light source for coherent detection is generated by a central node and transmitted to the user end along with the quantum light signal, or is generated by an independent laser source at the user end.

5. The downlink CV-QKD access network method based on wavelength division multiplexing according to claim 1, It is characterized in that The data processing includes phase compensation, polarization compensation, other link damage compensation, basis vector comparison, parameter estimation, data negotiation, error correction and private key amplification of the detected quantum signal.

6. A downlink CV-QKD access network system based on wavelength division multiplexing, comprising a central node and a user end, wherein the central node is connected to the user end via a transmission link; The central node includes M light source modules, a wavelength division multiplexing module, a continuous variable quantum light and reference signal generation module, and an electrical signal generation module. The M light source modules can generate at least N optical carriers with different wavelengths, and synthesize them into a beam of multi-wavelength carriers through the wavelength division multiplexing module; the electrical signal generation module generates an electrical signal containing original key information, and the electrical signal and the multi-wavelength carrier are modulated in the continuous variable quantum light and reference signal generation module to generate the required modulated quantum light signal and reference signal, and send them to the transmission link; The user end includes a wavelength division multiplexing module and N users. The wavelength division multiplexing module demultiplexes the received modulated quantum optical signal and distributes it to N users. Each user uses coherent detection to measure the quantum signal and performs digital signal processing on the detected quantum signal through a reference signal to complete quantum key distribution. The continuous variable quantum light and reference signal generation module includes a beam splitter, an electro-optical modulation module, a delay control module, a first optical attenuation module, a second optical attenuation module, a first polarization control module, a second polarization control module and a polarization combiner; the multi-wavelength carrier output by the wavelength division multiplexing module is divided into two paths by the beam splitter, one of which is processed by the electro-optical modulation module, the first optical attenuation module, and the first polarization control module in sequence and enters the polarization combiner, and the other is processed by the delay control module, the second optical attenuation module, and the second polarization control module in sequence and enters the polarization combiner, and is output after being combined by the polarization combiner; wherein the electro-optical modulation module also simultaneously receives the electrical signal of the original key information generated by the electrical signal generation module, and modulates the electrical signal onto the multi-wavelength carrier.

7. The downlink CV-QKD access network system based on wavelength division multiplexing according to claim 6, It is characterized in that The electrical signal generating module comprises a random signal generating module, a coding module, a digital-to-analog conversion module and a driving amplification module which are connected in sequence.

8. The downlink CV-QKD access network system based on wavelength division multiplexing according to claim 6, It is characterized in that When users measure quantum signals, they use homodyne or heterodyne coherent detection. The local oscillator light source for coherent detection is generated by a central node and transmitted to the user end along with the quantum light signal, or, it is generated by an independent laser source at the user end.

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