Quantum key distribution system capable of long-distance common-fiber transmission with classical optical communication system

Abstract

The utility model discloses a quantum key distribution system capable of long-distance common-fiber transmission with a classical optical communication system. The quantum key distribution system is designed to work in the 1350nm wave band, and compared with a conventional scheme adopting the 1310nm wave band, the quantum key distribution system has the advantage that a smaller optical fiber attenuation coefficient can be obtained. Moreover, by deploying a pair of narrow-band filters at the transmitting terminal and the receiving terminal of the QKD equipment, compared with a conventional scheme, the method has the advantages that lower loss can be realized at the receiving terminal of the QKD equipment while the noise is reduced, so that higher signal receiving efficiency is realized. Therefore, when the quantum key distribution system and a classical optical communication system carry out common-fiber transmission, the light intensity of the classical optical communication system does not need to be adjusted, and compared with a conventional scheme adopting a 1310nm wave band, the quantum key distribution system can obtain higher performance and longer transmission distance.

Description

Technical Field

[0001] The utility model relates to the field of quantum information technology, and particularly relates to a quantum key distribution system capable of co-fiber transmission with a classical optical communication system over a long distance. Background Art

[0002] A quantum key distribution (QKD) system, based on the principles of quantum non-clonability and uncertainty, can provide high-level information security protection and resist high-computing-power cracking. Since the signal light in the quantum key distribution process is very weak, usually at the single-photon level, when it is transmitted from the transmitting terminal to the receiving terminal through the link, the weak noise signal in the link has an obvious impact on the signal light. For this reason, early quantum key distribution systems often needed to use a dedicated optical fiber link alone to avoid the influence of other optical signals on the signal light.

[0003] To save link resources, related technologies for transmitting classical optical communication signals and quantum key distribution signals in the same link have been developed. Currently, there are mainly the following implementation methods: one is to attenuate the classical optical signal to reduce the noise generated by it; the second is to increase the wavelength interval between the classical optical signal and the quantum optical signal to reduce the generated noise; the third is to add a narrowband filter at the receiving terminal to filter out part of the noise.

[0004] Figure 1 Shows a device and method for multiplexing optical fiber transmission of quantum signals and classical signals in the prior art. By setting an optical intensity adaptive adjustment device communicatively connected to the QKD receiving terminal between the classical signal input module and the first wavelength division multiplexer, the optical intensity adaptive adjustment device automatically adjusts the attenuation coefficient according to the noise feedback information of the QKD receiving terminal to attenuate the classical signal.

[0005] Figure 2 Shows another device and transmission method for co-fiber transmission of quantum light and classical light in the prior art. It designs a narrowband filter at the receiving terminal to reduce noise; and designs a wavelength conversion device at the transmitting terminal to convert the classical light to a wavelength with a large interval from the quantum light, such as using a wavelength of 1550 nm in the C band for quantum light and using a wavelength of 1310 nm or 1625 nm for classical light.

[0006] Figure 3 Shows yet another method and device for classical quantum wavelength division multiplexing. It realizes co-fiber transmission of classical optical signals and quantum optical signals through a multiplexer and a demultiplexer in a specific wavelength band, and reduces the influence of Raman scattering noise of classical optical signals on quantum optical signals by allocating the wavelengths of classical optical signals and quantum optical signals.

[0007] However, the purpose of the field to transmit classical optical communication signals and quantum key distribution signals in the same link is to save link resources. In particular, it is hoped that quantum key distribution signals can be transmitted based on the existing optical fiber network for classical optical communication. Therefore, as little modification as possible or even no modification should be made to classical optical communication devices.

[0008] Based on this, it can be found that the existing implementation scheme based on attenuating classical optical power is limited in many practical application scenarios due to the high requirement for the receiving sensitivity of classical optical communication devices, and there may not be enough power adjustment space in the existing optical fiber network.

[0009] For the implementation method of reducing noise by increasing the wavelength interval between classical optical signals and quantum optical signals, the classical optical communication backbone network often uses the C band, and some have already used the L band at the same time. Eventually, with the increase in bandwidth, using the C band and the L band simultaneously will be the trend. Therefore, in order to pursue a large wavelength interval between quantum light and classical light, the 1310nm band is currently used in many specific schemes. However, the transmission loss of the 1310nm band in optical fiber is approximately 0.35dB / km. For a system that can tolerate 25dB of loss, using the 1310nm band can only transmit 71km, resulting in a significant performance reduction and making it difficult to apply in many current site locations (with a site distance of 80km).

[0010] For example, in the implementation scheme disclosed in the literature "Ultra-high bandwidth quantum secured data transmission", a 25GHz narrowband filter is adopted, and both quantum light and classical light are selected in the C band (with an interval of about 20nm), which requires reducing the power of classical light. In this implementation scheme, it is proposed to adjust the single-channel power to -25.5dBm, and the total power is approximately -15.5dBm when using 10 channels. Currently, optical communication backbone network devices often reach 80 waves, 110 waves or even more, and the input optical power reaches +21dBm or even higher. When adopting the implementation scheme proposed in this literature, the power of conventional optical communication devices needs to be reduced by approximately 36.5dB (corresponding to more than 4000 times), which is almost impossible to achieve in practical engineering applications.

[0011] In the implementation scheme disclosed in the literature "Integrating quantum key distribution with classical communications in backbone fiber network", a narrowband filter with a frequency of 20 GHz is adopted and there is no need to reduce the classical optical power. Quantum light and classical light are configured in bands with a relatively large wavelength separation to reduce noise (the quantum light is in the 1310 nm band, and the classical light is in the C band, with a wavelength separation of approximately 240 nm). Finally, only a co-fiber transmission distance of 66 km can be achieved.

[0012] In the implementation scheme disclosed in the literature "Co-propagation of 6 Tb / s (60 * 100 Gb / s) DWDM & QKD channels with ~17 dBm aggregated WDM power over 50 km Standard Single Mode Fiber", the quantum optical signal is in the 1310 nm band, and the classical optical communication is in the 1550 nm band, and the optical intensity is attenuated to 16 dBm. Finally, only a co-fiber transmission distance of 70 km can be achieved.

[0013] Generally speaking, in the currently disclosed co-fiber transmission schemes for classical-quantum signals, it is often necessary to reduce the classical signal power or set the quantum light wavelength in the 1310 nm band. Reducing the classical signal power means more requirements for classical devices, which hinders the practical application of the co-fiber transmission technology for classical-quantum signals. However, setting the quantum light wavelength in the 1310 nm band results in a large transmission loss in the optical fiber, and the performance of the quantum key distribution system is significantly reduced. Summary of the Invention

[0014] To solve the deficiencies in the above existing implementation schemes, the present invention discloses a quantum key distribution system that can co-fiber transmit with a classical optical communication system over a long distance. Among them, by designing the quantum key distribution system to operate in the 1350 nm band, a smaller fiber attenuation coefficient can be obtained compared with the conventional scheme using the 1310 nm band. Moreover, by deploying a pair of narrowband filters at the transmitting and receiving terminals of the QKD device, compared with the conventional scheme, smaller losses can be achieved at the receiving terminal of the QKD device while reducing noise, thereby realizing a higher signal reception efficiency. Therefore, when the quantum key distribution system of the present invention co-fiber transmits with a classical optical communication system, it is not necessary to adjust the optical intensity of the classical optical communication system, and higher performance and a longer transmission distance can be obtained compared with the conventional scheme using the 1310 nm band.

[0015] Specifically, the quantum key distribution system capable of co-fiber transmission with a classical optical communication system over a long distance of the present utility model may include a QKD device sending terminal and a QKD device receiving terminal, as well as a classical quantum wavelength division multiplexing component and a classical quantum demultiplexing component connected through an optical fiber channel;

[0016] The QKD device sending terminal is configured to modulate and generate a quantum optical signal having a first wavelength;

[0017] The classical quantum wavelength division multiplexing component is configured to perform wavelength division multiplexing on the quantum optical signal and a classical optical signal to form a combined beam of light for input into the optical fiber channel;

[0018] The classical quantum demultiplexing component is configured to demultiplex the combined beam of light from the optical fiber channel to obtain the quantum optical signal and the classical optical signal;

[0019] The QKD device receiving terminal is configured to demodulate and perform single-photon detection on the quantum optical signal obtained through demultiplexing;

[0020] The first wavelength is between 1345 nm and 1355 nm;

[0021] The QKD device sending terminal further includes a first narrowband filtering module for filtering the optical signal, and the QKD device receiving terminal further includes a second narrowband filtering module for filtering the quantum optical signal obtained through demultiplexing, and the bandwidth of the first narrowband filtering module is less than or equal to the bandwidth of the second narrowband filtering module.

[0022] Preferably, the first wavelength is 1350 nm.

[0023] Preferably, the bandwidth of the first narrowband filtering module is 5 - 10 GHz.

[0024] Preferably, the bandwidth of the second narrowband filtering module is 5 - 10 GHz.

[0025] Preferably, the first narrowband filtering module includes an FP cavity filter or a fiber grating.

[0026] Preferably, the second narrowband filtering module includes an FP cavity filter or a fiber grating.

[0027] Preferably, the optical fiber channel includes G652.D optical fiber.

[0028] Furthermore, the QKD device sending terminal includes a light source having a first wavelength and a quantum state modulation module; the QKD device receiving terminal includes a quantum state demodulation module and a single-photon detection module.

[0029] Preferably, the light source is a semiconductor laser.

[0030] Preferably, the single-photon detection module is a single-photon detector. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The following further describes in detail the specific embodiments of the present invention with reference to the drawings.

[0032] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or in the prior art, the following briefly introduces the drawings required for use in the description of the embodiments or the prior art. Obviously, the following-described drawings are only some embodiments of the present invention, and for those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0033] Figures 1-3 Several classic-quantum wavelength division multiplexing schemes in the prior art are respectively shown;

[0034] Figure 4 A preferred example of a quantum key distribution system capable of co-fiber transmission with a classic optical communication system over a long distance according to the present invention is shown;

[0035] Figure 5 A graph showing the actual attenuation coefficient of quantum optical signals in an optical fiber channel in the quantum key distribution system according to the present invention is shown. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0036] In the following, the exemplary embodiments of the present invention will be described in detail with reference to the drawings. The following embodiments are provided by way of example to fully convey the spirit of the present invention to those skilled in the art to which the present invention pertains. Therefore, the present invention is not limited to the embodiments disclosed herein.

[0037] Figure 4 A preferred example of a quantum key distribution system capable of co-fiber transmission with a classic optical communication system over a long distance according to the present invention is shown.

[0038] As shown in the figure, the quantum key distribution system includes a QKD device sending terminal, a classic-quantum wavelength division component, a classic-quantum demultiplexing component, and a QKD device receiving terminal. Among them, the classic-quantum wavelength division component and the classic-quantum demultiplexing component are connected through an optical fiber channel.

[0039] On the sending side, the QKD device sending terminal modulates the optical signal into a quantum state to generate a quantum optical signal. The classic-quantum wavelength division component forms a combined beam of light by wavelength division multiplexing the quantum optical signal generated by the QKD device sending terminal and the classic optical signal generated by the classic optical communication device, and outputs the combined beam of light to the optical fiber channel to send to the receiving side.

[0040] On the receiving side, the combined light beam reaches the classical and quantum demultiplexing component through the optical fiber channel, and the quantum optical signal and the classical optical signal are obtained through demultiplexing, and the classical optical signal and the quantum optical signal are respectively transmitted to the classical optical communication device and the receiving terminal of the QKD device.

[0041] In the receiving terminal of the QKD device, the quantum optical signal is detected by the single-photon detection module after demodulation processing.

[0042] The inventors conducted research by breaking through the inherent thinking in this field and found that by selecting the wavelength of the quantum optical signal (i.e., the first wavelength) within a specific wavelength range, that is, between 1345 nm and 1355 nm, especially in the 1350 nm band, it is allowed to further improve the performance and working distance of the QKD system on the premise of meeting the co-fiber transmission of wavelength division multiplexing.

[0043] Figure 5 The actual attenuation coefficient curve of the quantum optical signal in the optical fiber channel in the quantum key distribution system according to the present invention is shown. It can be seen from this that in the 1350 nm band, the attenuation of the quantum optical signal in the optical fiber channel is reduced by about 15% or even more compared with the attenuation coefficient in the conventional 1310 nm band. For example, in the widely used G652.D optical fiber in the current network, the link attenuation coefficient in the 1350 nm band is about 0.3 dB / km, while the link attenuation coefficient in the 1310 nm band is 0.35 dB / km, and the link attenuation coefficient is reduced by about 15%.

[0044] Based on this research, a light source with the above first wavelength can be set in the transmitting terminal of the QKD device of the present invention to provide an optical signal with the first wavelength.

[0045] As a preferred example, the light source can be a semiconductor laser.

[0046] In the transmitting terminal of the QKD device, the quantum state modulation module can work in the first wavelength band to perform quantum state modulation on the optical signal generated by the light source to generate a quantum optical signal with the first wavelength.

[0047] In the present invention, a first narrowband filtering module can also be set in the transmitting terminal of the QKD device to perform narrowband filtering on the optical signal output by the light source or the quantum state modulation module, thereby further reducing the system noise.

[0048] In a preferred example, the bandwidth of the first narrowband filtering module can be 5 - 10 GHz.

[0049] In a preferred example, the first narrowband filtering module can be an FP cavity filter or an optical fiber grating.

[0050] According to the present utility model, a second narrowband filtering module can be arranged in the receiving terminal of the QKD device for performing narrowband filtering on the received quantum optical signal.

[0051] In a preferred example, the bandwidth of the second narrowband filtering module can be 5 - 10 GHz.

[0052] In a preferred example, the second narrowband filtering module can be an FP cavity filter or an optical fiber grating.

[0053] According to the present utility model, the bandwidth of the first narrowband filtering module can be set to be less than or equal to the bandwidth of the second narrowband filtering module, ensuring that the quantum optical signal can better pass through the second narrowband filtering module, thereby further reducing the loss of the quantum optical signal in the receiving terminal of the QKD device and overall achieving a smaller loss.

[0054] Continue to refer to Figure 4 , in the receiving terminal of the QKD device, the quantum state demodulation module can operate in the first wavelength band to demodulate, for example, the narrowband-filtered quantum optical signal, and the demodulated quantum optical signal finally enters a single-photon detection module (such as a single-photon detector) for single-photon detection.

[0055] Based on the above, for the current conventional implementation schemes such as needing to attenuate the power of classical optical communication devices or configuring the wavelength of QKD devices in the 1310 nm band, etc., in practical applications, there are problems such as the need to transform classical optical communication devices or quantum key distribution devices because the 1310 nm optical signal has a large loss in optical fibers, resulting in reduced performance and hindering practical engineering applications. The present utility model designs the quantum key distribution system to operate in the 1350 nm band, which has a smaller attenuation coefficient in optical fibers compared to the conventional 1310 nm band; and by designing a pair of narrowband filters, compared to the conventional scheme, it can achieve a smaller loss at the receiving terminal of the QKD device while reducing noise, and achieve a higher signal reception efficiency. Therefore, when the quantum key distribution system of the present utility model is co-fiber transmitted with the classical optical communication system, it can be unnecessary to adjust the optical intensity of the classical optical communication system, and can obtain higher performance and a longer transmission distance compared to the conventional 1310 nm scheme. More importantly, with the increase in the co-fiber transmission distance (which can reach more than 80 km with the scheme of the present utility model), it will be able to meet the distances of most current existing sites, enabling the quantum key distribution device to directly use the existing network optical fiber resources, greatly reducing the deployment cost of the quantum key distribution device, promoting the application of the quantum key distribution device, and providing information security protection for more users.

[0056] Although the present utility model has been described above in conjunction with the accompanying drawings through specific embodiments, it is easy for those skilled in the art to recognize that the above embodiments are merely exemplary and are used to illustrate the principle of the present utility model, and they will not limit the scope of the present utility model. Those skilled in the art can make various combinations, modifications, and equivalent replacements to the above embodiments without departing from the spirit and scope of the present utility model.

Claims

1. A quantum key distribution system capable of co-fiber transmission with a classical optical communication system over a long distance, which includes a QKD device transmitting terminal and a QKD device receiving terminal, as well as a classical quantum wavelength division multiplexing component and a classical quantum demultiplexing component connected through an optical fiber channel; The QKD device transmitting terminal is configured to modulate and generate a quantum optical signal having a first wavelength; The classical quantum wavelength division multiplexing component is configured to perform wavelength division multiplexing on the quantum optical signal and a classical optical signal to form a combined beam of light for input into the optical fiber channel; The classical quantum demultiplexing component is configured to demultiplex the combined beam of light from the optical fiber channel to obtain the quantum optical signal and the classical optical signal; The QKD device receiving terminal is configured to demodulate and perform single-photon detection on the quantum optical signal obtained by demultiplexing; It is characterized in that: The first wavelength is between 1345 nm and 1355 nm; The QKD device transmitting terminal further includes a first narrowband filtering module for filtering an optical signal, and the QKD device receiving terminal further includes a second narrowband filtering module for filtering the quantum optical signal obtained by demultiplexing, and the bandwidth of the first narrowband filtering module is less than or equal to the bandwidth of the second narrowband filtering module.

2. The quantum key distribution system according to claim 1, wherein The first wavelength is 1350 nm.

3. The quantum key distribution system according to claim 1, characterized in that, The bandwidth of the first narrowband filtering module is 5 GHz - 10 GHz.

4. The quantum key distribution system according to claim 1, characterized in that The bandwidth of the second narrowband filtering module is 5 GHz - 10 GHz.

5. The quantum key distribution system according to claim 1, characterized in that, The first narrowband filtering module includes an FP cavity filter or a fiber grating.

6. The quantum key distribution system according to claim 1, wherein The second narrowband filtering module includes an FP cavity filter or a fiber grating.

7. The quantum key distribution system according to claim 1, characterized in that The optical fiber channel includes G652.D optical fiber.

8. The quantum key distribution system according to any one of claims 1-7, characterized in that, The QKD device transmitting terminal includes a light source having a first wavelength and a quantum state modulation module; the QKD device receiving terminal includes a quantum state demodulation module and a single-photon detection module.

9. The quantum key distribution system according to claim 8, wherein, The light source is a semiconductor laser.

10. The quantum key distribution system according to claim 8, wherein, The single-photon detection module is a single-photon detector.

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